Can we agree on a couple of things here??
OP is 183cm tall and 66kg.
He needs to gain weight.
He needs to train for maximal results.
Why are people really advising that he does split routines or 5-6 days a week or forearm curls for the nice burn etc etc?
seriously, the guy could eat a bowl of lard 5 times a day for 12 weeks and still look skinny.
does anyone here really disagree that this is the perfect scenario for 5x5 of squats/bench/dead/overhead press/chins/rows and nothing more?
also, what ever diet he posts, each of the 3-6 meals he has per day should have about 500ml of full cream milk to wash it down.
6ft tall and 66kg.
I know a guy that had an eating disorder.
He became anorexic.
once he got his mind straight, he did 5x5 for a year and ate everything.
went from 43kg at 6ft to 100kg.
his current lifts are
squat 180
bench 140
dead 230
now he's taking some time off from 5x5 to do some BB type stuff to give his joints a break to recover etc.
but the point is, size comes from heaps of food and big movements.
3 times week is perfect.
OP - if you do splits and time wasting lifts like forearm curls or tricep kick backs etc, you will be 66kg and 6ft when you are 24 too.