Can I patent an idea to make something better than it currently is?

It is possible to obtain a patent on an improvement. However, obtaining a patent does not mean that you do not infringe on someone else's patent. If you patent an improvement on someone else's technology, it may be possible to do a cross-license deal with them so you have permission to use their technology and they have your permission to use your improvement. However, they are not obligated to use your technology and to give you a cross license.