New functions for an existing community [PHP, SQL, JAVASCRIPT]

Hello programmers, bought a german fun community some days ago and now this community need some new functions and a performance upgrade. Some things that have to be done: - Youtube Thumbnail Upload function - User Invite System - filters (gif / youtube video / other pictures) - performance update - there are some very slow AJAX/JS functions - new comment-function - and many more little things There is much work todo and there will be more work in the future. So I'm looking for a "lifelong" programmer at my side. Show me your last references / work and please only apply if you can code PHP / JS and SQL! Thank you!