I dropped my phone in the bath and now my data (4G) wont work properly

@tegan_ricara

if you continue to use it, it will stop to “still works slightly” pretty quickly.  You have a water damaged phone and are running risk to further damage it by using it.

Remove your battery and you’ll need to disassemble your phone. Use something like this guide Samsung Galaxy J5 (2016) Disassembly but it starts at the end of the disassembly. Once you have it disassembled you need to clean it. Use this guide iPhoneの水濡れ･水没ダメージからの復旧方法 for that. It was written for an iPhone but all the points still apply to your phone as well. Once it is properly cleaned you want to go ahead and repalce the battery. Reassemble your phone and then re-evaluate. Only after a proper cleaning can one make teh determination what may have failed. yours appears to be an antenna/RF issue and may require the help of somebody who specializes in board level repair.