Prestashop website expert (not beginners-intermediate) needed

Our website is having a couple issues which we need to solve without taking it down. In the evenings, from 8 pm, the admin side starts to freeze, so that even the admin can't get in. If you try to go to our other e-store or anywhere else at the same time , you will have no problems and everything will run smoothly and quickly. For example, when moving from order to order, you sometimes have to wait minutes, 2-3.5 minutes, before moving on. However, for some time it passes and can work normally. We thought maybe there was a problem with the computer or the internet and experimented with different computers and still had the same problem on another network . This problem occurred in the first week of December and after dealing with cached files some code was written there. After that, the store is no longer closed, but it became slow in the evenings and began to freeze. other changes here [login to view URL] Please bid only if you are capable of solving all