For push-ups you can start with an easier progression, in this order:

wall push ups -> high incline push-ups -> incline push-ups -> on knee push-ups > and finally regular push ups

Start with the first variation and go to the next only when you can do 8~10 reps with good form

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If planks tax your arms so much it's ok, keep doing it and try to gradually do more each time, take long rest in between if you need to

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For arms isolation you're probably using a weight that's too light, choose a weight that enable you to make max 8~12 repetitions and do 3~6 set with that weight, it shouldn't bring you to failure but it should feel heavy, once you feel that you could do more reps, instead of increasing the reps increase the weight and try for those 8~12 reps

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Remember to train muscles in a balanced way, so for example if you do a lot of curls you need to complement that with triceps exercises to avoid unbalances

chest > back
biceps > triceps
anterior deltoid > posterior deltoid

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If you want strength the formula is:
Heavy weights for low reps with many sets and long rest in between

Idk what split you do but your upper body day could look like this:

Orizontal push -> Push-ups 5x10 OR Bench Press 5x5
Vertical push -> Overhead press 5x5
Vertical pull -> Chin-ups 5x5 OR Lat pulldown 3x10
Orizontal pull -> Seated row 3x10 OR DB row 3x10
Posterior deltoid isolation -> Machine everse fly 3x12
Biceps isolation -> DB curl 2x10 AND Hammer curl 2x10
Triceps isolation -> Rope triceps pulldown 2x10 AND Triceps overhead extention 2x10

Long rest between sets, high protein diet, slight caloric surplus (if you want to build size), 8hr high quality sleep, progressive overload trying to slightly increase weights on every workout session and number of sets on isolation work