so I have been having a problem with my Samsung Galaxy S5 where it runs really slow on my wifi but mobile data runs fine. Now before anyone says it's my crappy wifi it's not I have a 50 up and 50 down with a 12 ping. I also have a couple of really old phones that I tested my wifi signal with and they work fine. I tried resetting the router and resetting the phone to factory settings nothing worked. So that tells me it's more than likely my wifi antenna. So now the question is how do I or how much does it cost to get it fixed? Or would I just be better off buying a new phone?

Also if I posted this in the wrong subreddit i'm sorry i'm relatively new to reddit so I'm not sure if I'm in the right subreddit
Any help is appreciated Thanks