I plan on going to the gym 4-5 times a week. I've done mentzer's method (push till failure) and also gradually lowering weight in between sets (1st set highest - weight, 3rd - the lowest weight).

What's the best method to do? How many sets, reps and how many exercises per muscle group.

I plan on doing push-pull-legs, but I wonder how many sets do I need to do and in which way. Should I lower weights and do 8-10 reps each or should I go for 2 sets max and both till failure?

I've heard some dudes go for 40-50 reps, but that's absurd. The normal workout varies between 4-6 reps for 2 sets for failure and for normal workout 10-12 reps for 3-4 sets.

Also, I plan on doing incline treadmill on about 12-15 incline and 3 speed and that for about 20-30 minutes after the normal workout of 30 minutes. Since the bike isn't as effective (apparently you burn less fat since you don't move the whole body so it's easier) or is it?

I know I need to lose fat and build muscle (for skinny fat type). For eating I'd be in maintenance or a slight surplus and drink 3-4 litres of water a day.

P.S. I'd like to hear some advice on building muscle on forearms since that's my biggest weakness and insecurity. I've found it hard to grow muscle here and to effectively hit all 3 types of muscles located in forearms.

With the straight bar it's not as effective, dumbbells seem to do fine, but it's not as effective as building chest and triceps imo.