Current problem is about changing filament. The second layer doesnt stick to the first one after changing filament. Exmp. on the pic below. Any advices?
Hello @mkzor56 …! 
Welcome to the Creality Forum…! 
Judging by the first layer in your picture (the brim part) the nozzle needs to be closer to the bed. It is not squishing down each layer so they will have trouble sticking to each other.
Try adjusting the Z offset.
What filament and temps are you using…?
PLA filament. 230 C