should I replace a battery with an already lifted screen?

Rahaul k you got a whole bunch of issues going on here. You want to proceed in a somewhat logical manner. Your battery is most likely expanding due to it having failed through the water damage. So the very first thing you want to do is to not try to restart the phone sync it or otherwise continue to use it. This may further damage your phone. The next thing to do is to clean it. Disassemble your phone using this guide Then clean it with +90% isopropyl alcohol. You must remove all the EMI shields. You can not properly clean it with those on. Follow this guide, and even so it was written for a 3G all the points are still pertinent to your phone. Yes, you can soak the complete board in isopropyl alcohol. While you clean your board, check for any obvious damage, like burned or missing components etc. Double check your battery connector. When it is properly cleaned, you must replace the battery. In your case you also want to repalce the complete display assembly. A glass only repair for a novice is a hard chore and almost guaranteed to fail the first couple of times. Use this guide to replace the assembly. All these steps are to avoid delayed failure caused by corrosion., which your phone is already showing. Once all this is done, reassemble your phone and reevaluate.