Hey guys,
First I want to say that I am a total newbie. I literally received the batteries for my drone today and was excited that I was succesful in binding my Nazgul5 V2 with my Taranis QX7.
Then I remembered a video of Joshua Bardwell about betaflight. So with the help of this link:  I tried getting everything setup. 
I installed all drivers and had everything running.
The drone seemed properly connected but then I heard Joshua say, that I should flash it. So AFTER making a backup of the default settings (which I still have), I flashed it. 
The bootloader worked fine and I selected the correct target: STM32F7X2 I selected the newesr version and the flashing and installing started.
Everything worked fine. The drone reconnected to my pc and then I noticed the first issue: 
I got a warning that there was no motor protocol selected. 
I closed it and immediately noticed something else, the gyro and accelerometer (in the top bar) weren´t yellow anymore. So basically Betaflight doesn´t seem to receive any gyro info, because when I move the drone. The 3D visualization just sits perfectly still. This wasn´t the case before flashing it.
   

Then I proceeded into the port section and noticed that there is not a single UART port being listed. (I don´t know if there were any before flashing).
   

I haven´t even looked further into BF, because I first wanted to fix the gyro/acc issue. So the first thing that came to mind was just trying to reinstall the original file. So I went into CLI and tried doing exactly that via the `load from file` option. Then this happend:
2021-03-10 @ 23:44:43 -- CLI mode detected
2021-03-10 @ 23:45:08 -- CLI reboot detected
2021-03-10 @ 23:45:08 -- Device - Rebooting
2021-03-10 @ 23:45:08 -- Unrecoverable failure of serial connection, disconnecting...
2021-03-10 @ 23:45:08 -- Failed to close serial port

And now I´m sitting here with my new drone. Realizing that I NEED HELP. What did I do wrong and how can I fix it. I really hope that I didn´t screw anything up.
Thanks you all for taking the time and reading all my stupidity.

You've flashed the wrong Betaflight target. The STM32F7X target is a generic base target for all F7 flight controllers. You need to flash the specific F7 target for your particularalr FC.

Open the "diff all" you saved with your previous settings in and at the top it will have the target name you need to use. If you're not sure, post that "diff all" file back here and we can tell you what target you need.

After flashing the target and connecting for the first time, you will be prompted about applying custom defaults. Make sure you click the "Apply Custom Default" button.

I really didn´t expect such a quick reply. THANKS.
Here is my diff all:
# 

# diff all

# version
# Betaflight / STM32F7X2 (S7X2) 4.2.4 Oct 20 2020 / 08:20:06 (fbcaf8c50) MSP API: 1.43
# config: manufacturer_id: IFRC, board_name: IFLIGHT_SUCCEX_E_F7, version: c7fde51e, date: 2020-08-26T04:30:34Z

# start the command batch
batch start

# reset configuration to default settings
defaults nosave

board_name IFLIGHT_SUCCEX_E_F7
manufacturer_id IFRC
mcu_id 001f000b345650032030324b
signature 

# name: Nazgul5 V2

# feature
feature -SOFTSERIAL
feature TELEMETRY
feature LED_STRIP

# beacon
beacon RX_LOST
beacon RX_SET

# serial
serial 0 8192 115200 57600 0 115200

# led
led 0 0,0::L:0
led 1 1,0::L:0
led 2 2,0::L:0
led 3 3,0::L:0

# aux
aux 0 0 0 1700 2100 0 0
aux 1 1 1 900 2100 0 0

# vtxtable
vtxtable bands 5
vtxtable channels 8
vtxtable band 1 BOSCAM_A A CUSTOM  5865 5845 5825 5805 5785 5765 5745 5725
vtxtable band 2 BOSCAM_B B CUSTOM  5733 5752 5771 5790 5809 5828 5847 5866
vtxtable band 3 BOSCAM_E E CUSTOM  5705 5685 5665 5665 5885 5905 5925 5925
vtxtable band 4 FATSHARK F CUSTOM  5740 5760 5780 5800 5820 5840 5860 5880
vtxtable band 5 RACEBAND R CUSTOM  5658 5695 5732 5769 5806 5843 5880 5917
vtxtable powerlevels 4
vtxtable powervalues 25 100 400 600
vtxtable powerlabels 25 100 400 800

# master
set acc_calibration = 28,57,109,1
set mag_hardware = NONE
set baro_hardware = NONE
set blackbox_p_ratio = 16
set dshot_idle_value = 600
set dshot_bidir = ON
set motor_pwm_protocol = DSHOT300
set vbat_max_cell_voltage = 440
set yaw_motors_reversed = ON
set small_angle = 180
set pid_process_denom = 2
set osd_rssi_pos = 2390
set osd_link_quality_pos = 310
set osd_rssi_dbm_pos = 299
set osd_tim_2_pos = 2453
set osd_flymode_pos = 2413
set osd_vtx_channel_pos = 2421
set osd_current_pos = 2400
set osd_mah_drawn_pos = 2432
set osd_craft_name_pos = 2445
set osd_warnings_pos = 14666
set osd_avg_cell_voltage_pos = 2369
set osd_disarmed_pos = 2336
set debug_mode = GYRO_SCALED
set vtx_band = 5
set vtx_channel = 3
set vtx_power = 1
set vtx_freq = 5732
set gyro_1_sensor_align = CW270
set gyro_1_align_yaw = 2700
set name = Nazgul5 V2

profile 0

# profile 0
set dyn_lpf_dterm_min_hz = 98
set dyn_lpf_dterm_max_hz = 238
set dterm_lowpass2_hz = 210
set vbat_pid_gain = ON
set anti_gravity_gain = 4500
set iterm_relax_cutoff = 10
set yaw_lowpass_hz = 70
set p_pitch = 55
set d_pitch = 41
set f_pitch = 124
set p_roll = 50
set d_roll = 38
set f_roll = 117
set p_yaw = 54
set f_yaw = 117
set d_min_roll = 25
set d_min_pitch = 27

profile 1

profile 2

# restore original profile selection
profile 0

rateprofile 0

# rateprofile 0
set rates_type = ACTUAL
set roll_rc_rate = 19
set pitch_rc_rate = 19
set yaw_rc_rate = 19
set roll_expo = 60
set pitch_expo = 60
set yaw_expo = 60
set roll_srate = 90
set pitch_srate = 90
set yaw_srate = 90

rateprofile 1

rateprofile 2

rateprofile 3

rateprofile 4

rateprofile 5

# restore original rateprofile selection
rateprofile 0

# save configuration
save
#

You need to flash the IFLIGHT_SUCCEX_E_F7 target to your FC.

Don't forget to "Apply Custom Defaults" after doing that when you first connect Betaflight to the FC after having successfully flashed the board.

You know what SnowLeopardFPV, you are already a legend to me. That just totally fixed it. 
I appreciate it man!

No problem. Happy flying

I am still in the process of setting up Betaflight. Can someone explain why after I have increase throttle on my controller and then lower it again, the quad keeps increasing motor speed (even if throttle is all the way down)? I am a little confused, again .

If you are testing the motors with props off on the bench then that behaviour is normal. Have a watch of the following video to understand why...

Ah, sweet. that makes sense, even tough mine doesn´t even stop spinning when I put the throttle is at 0. Only way to stop them for spinning faster and faster is to disarm.

But like Joshua said, I´ll do a hover test to find out if it´s an issue. Thanks once again.