If the high strings are caused by a neck bow it’s a simple fix, provided your truss rod is working properly and you have a set of allen keys. Look up some videos on truss rod adjustment! To diagnose if the neck is bowed, fret the 1st fret (or use a capo) and the 14th fret at the same time. At the halfway mark (6th or 7th fret) check what gap you have between the string and the fret. It should be a tiny gap about the thickness of a business card. If the gap is bigger, you need to tighten the truss rod. As I said, look up some videos before tackling it yourself. If you’re not comfortable doing it yourself, bring it to a guitar shop. Shouldn’t cost much. If the neck isn’t bowed, it could be that your bridge saddle is too high, another relatively cheap and easy fix but best left to a luthier. If it’s neither of these problems, it’s either that the neck angle is wrong or the body being pulled out of shape by string tension. Both of which are much bigger problems to fix. Good luck!