Body part split is not recommended, because many body parts overlapped in performing a particular movement. Example, you are gonna work the chest and triceps if you bench press. Go for Push (triceps, chest, front delt)/Pull (back, biceps, rear delt)/Legs or Upper/Lower split. Age would impact your recovery so make you have enough rest, and maybe - I'm no expert - 5days is an overkill.

And dang, didn't know you are that young!

What do you mean you split between biceps & triceps? I thought there is an arm day, during which you should do both? Also, that's actually already isolating the muscles... Maybe draft what do you do on each of your upper part days?

5 days is alright if you train less than an hour each time, assuming the intensity is on point. Can't be training long and not enough rest between sessions.

Oh then I understood you correctly, you are doing body parts split, therefore my point stands. You should do triceps on the same day you do chest (together with front delts), because both groups of muscles are required to perform pushing. Likewise for biceps & back (and rear delts), they are needed to pull. Doing what you are doing now, it might mean that your arms are being put on extra work by having to work on arm as well as back & chest day. That also mean that they might hamper your ability to train heavier/longer on the back & chest days. You are also short changing your back & chest muscles as you could not train them as frequently as you could if you adopt push/pull split. You can refer to my workout journal in my siggy if you don't mind, I use push/pull split.

That's quite a long workout, I fear you may not be able to keep it up in the long term, and consistency is the key to this game. But if you insist on doing that for now, maybe re-assess things should you find yourself getting tired despite having enough rest. I think recovery for 'young' people works differently.

I think high peaks of the biceps has more to do with genetics. Actually the long head creates the peak, not the short head...
While you might not want to increase poundage to your workout, like I said, training your arms in isolation would short change your back, chest & even shoulder workout. Though it's not recommended, but if arms are your sole focus then only you know better what do you really want, so up to you lar really.

Yeah, still about 63-64kg. Decided that I would go slow (like really slow) rather than bulk up then cut, because my bones are too small, and I couldn't bear the sight of me having a very visible tummy.

I do appear like I don't even lift if I wear loosely, but not very skinny, yet, I hope.

I would be 30 next year.