In general, the CiviCRM code is not that much slower than Wordpress, so something other than CPU is involved here. I'd suggest your two best lines of inquiry are:
If the slowness is very specific to after saving a new contact or making changes, then either your SQL server has way too much caching, or else you have some kind of slow extension/customization that is executing after the save (e.g. perhaps you've got geo-coding turned on and it's failing to communicate with that external service - many providers tend to block or slow down outgoing http requests, I've noticed).
If the slowness has no particular pattern to it, then it might be just running out of RAM (i.e. server memory). When that happens, servers get super slow as they swap stuff in and out to disk.
In any case, your first step is to get more diagnostic material. DON'T just start trying random fixes recommended by your brother-in-law - chances are that you could be muddying the waters and making things worse (or maybe that's how you got into this in the first place ...).