Yesterday I managed to try flying in radio virgin environment (far outside the city).
Completely disappointed...
The range is too fucking low...
Any ideas, how can I make sure that my Taranis x7 Lite is good?

How much range did you get? The onboard SPI Frsky D8 Receiver does suffer from range if that's what you are using for the RC link. I do not think its your Transmitter.

i didnt read the whole thread, but place the spi antenna vertical does improve the signal on spi receivers. it could also brake away if its still partialy broken when you bend it and will need to solder it back and get the signal fully working.

My range is about 10-30 metres in open space.
Yes, antenna is a very tricky stuff. Vertical antenna is the best choice for objects moving around you. Its easy to do with transmitter. But with flexible antenna on onboard receiver its quite difficult.

That range is probably about right for an SPI receiver. They really do have quite poor range and are really designed to be flown inside a building or a very small park like area. A lot of people just fit an external full range receiver to whoops with an SPI receiver to get an extended range, but that obviously increases the weight quite a bit and thus also shortens the flight time a bit.