Should i keep lifting until i cannot lift it anymore? Or should i make sure i keep changing hands and follow sets obediently? Or should i stop when i got tired? Or shoupd i not stop and go over limit for muscle building effect?

You should do sets that is a determined number of reps then rest and then repeat.

Do not lift to failure. Normally want to use enough weight so you will do 3 sets of 8 to 10 reps, and have difficulty finishing the last set, if it becomes easy increase the weight.

If you can not change your weight then you must change the routine.

If you are doing single arm exercises you could alternate arms as the rest between sets.

Just do really hard to progress bodyweight excercises and then when you get lots of dumbbells weights so you can progress, if you dont progress you dont really build muscle. Go really low when you go down and when going up you explode with the dumbbell. Just now do one arm pushup and one leg squat

You should only be lifting maybe 2 more times after you feel you cannot go anymore.

ring it