Help plss

Guys I'm 19M 6ft and weigh about 83kgs. I started gym last july and didn't focus much on the diet and made slower progress and in Nov due to study load I couldn't go and then Ramadan came all that and I started again I wanna recomp and focus on diet but the thing is when I'm following a diet plan I tend to undereat I can get 100gm protein in But my calories mostly stay in like 16-1800 and I think due to this O can't give my fullest at the gym also