here you can find what kernel parameters exist drm/amdgpu AMDgpu driver — The Linux Kernel documentation but generally it should just work without fiddling.
I just found something - I was googling many issues and found somewhere CTRL+ALT+F2 and then startx command.
When I reproduce this issue (let TV turned off, turn on PC, wait for boot (i check over ssh), than turn TV on, there is black screen and nothing happens. But when I use that key combination, TV wakes up and wants login. When I log in and type startx, my desktop appears. So what is this issue? What does it mean?
After monitor has woken up, have you tried switching back to desktop (ctrl-alt-f1) ?
When switching to another virtual terminal the video mode changes, which might be what wakes up the monitor.
I already told that I am new to Linux desktop - so I didn´t because I dont know ctrl+alt+f1 
can you explain these shortcuts what do they do?
I tried, CTRL+ALT+F1 does nothing until I login and use startx
after that ctrl+alt+f1 takes me back to black screen and F2 to that desktop I just started.
F1 should be the first “virtual terminal” and F2 is the second. They go up to 7 IIRC so you can run different users in each of them. F1 should have your normal desktop session that is automatically started.