u/Easy-Librarian4597

Im new to the gym and i was wondering is it better to do 2sets until failure or 3 sets 8-12 reps. I wanna maximize my gains but also sometimes save on time cuz my gym is kinda far away. What should i pick?

Hi guys i need help with my workouts. Today i had a werid drop in strength on my shoulder press. This monday i was able to do 2 sets of 10-12 reps with 14 kg and 1 set with 16kg, 9 reps. Today i did shoulders again i coundt evan bring up the 16s and with 14s i was able to do 5 reps max. This isnt the first time something like this happend, my preacher curls were kinda in a similar state, bouncing between weight but it stoped happening there and now its my shoulders. I dont know what im doing and im in a really need of help. Also my split is ppl/ul.