Expert PHP 5 and MYSQL

Three years ago I started the website www.altijdbon.nl. A Dutch website that shows the best deals (product, events such like zoo deals and many more deals) that we can find each day on the internet. Why people visit [login to view URL] because we check each day if the deals are still availiable and we categorize deals, so people can find easily the deal that they’re looking for.. Now I’m looking for a new develop company. Unf. mine current developer can’t solve some speed issues and some other issues. Mine website is (sometimes) really slow and many times a day I use all mine memory usage, with the result that [login to view URL] is offline and the visitors get a 500 or 503 error. It’s weird that 90% of the time the website is working proper, but if I get many visitors the website is going offline. This happened 1,5 month ago, after some updates of mine current developer. Mine current developer give me the advice to get more memory, so I switched to GoDaddy Business Hosting (a product what you can compare with dedicated hosting with 4K memory usage).. More than enough space for a small website that I have… Even after this switch I have speed problems and people get still the 500 and 503 error. Now I’m quite sure it’s not the hosting plan, but I’m searching for someone who can find the issue. Godaddy informed me that the script creates processes but does not kill them, that leads to the memory usage being overloaded. I don’t have the knowledge what they mean, but I’m looking for a develop company that can help me with fixing this BIG issue. The last days I have as well other issues.. For example the last days data is leaking. For example I have deals categorized in a specific category, so people can find easily there deal. The last days the (sub)categories disappear without that I do something.. This really weird and I don’t know what’s happening. Someone has to check the script, [login to view URL] en [login to view URL], because in de [login to view URL] are errors that we have to solve.. If you can fix the speed issue and the errors I have for sure more work in the nearby future. For me it's important that if I have some new work that we can fix it soon or if there are some problems you can help me soon. Of course the quality of your work has to be great :-)...