Website slowing down

I noticed that sometimes when more than 50 users are online and using their wallet , the website becomes very slow.I made some research and found that this may be due to an abusive use of PHP unserialize() function in Terra wallet code instead of json_encode and json_decode. I don’t know enought but I really need this plugin to work fine so any help will be welcome. Sorry for bad english !

The page I need help with: [log in to see the link]