MYSQL CONFIGURATION EXPERT NEEDED

We have a high load server that is constantly going down. mysql tables are crashing multiple times a week (sometimes more) and are requiring to be repaired (we even setup a script to auto-repair tables because it happens so often). The server is a high-performance server with plenty of RAM but is still constantly having issues. Also, apache is often crashing and often when trying to reload httpd we see: Warning: The unit file, source configuration file, or drop-ins of [login to view URL] changed on disk. Run 'systemctl daemon-reload' to reload units. The database has 112 tables. Some of the tables have millions of rows. Most of the tables are MyISAM but the ones with a larger amount of rows are InnoDB. The tables have indexes setup. When having issues and checking top, normally mysql is 80-150% usage and memory is at 4-15% usage. Like at the time of writing it the server is "ok" but mysql has 10-40% CPU usage and only 2-4% memory usage. We need help with the following items: -- Optimizing mysql via the /etc/[login to view URL] file (and all sub files for mysql configuration) -- To know what we need to do to make the site scalable (do we need to put mysql on a separate server, setup load balancing, is it merely configuration, etc)? -- We need help identifying where the bottlenecks are. For example, maybe there is a query that is missing an index, but we are not seeing it. We have mysql_slow_query_log setup but it seems largely useless as the server gets a large load and then basically every query is slow, queries that are not an issue at all, and they end up on the report making the report hard to use to identify issues. We do not use CPanel/WHM/etc, everything is done in linux. We need to understand what is being done. We need you to explain briefly what/why you did changes. I am writing this for the owner of the site. I am the writer of the script. I am a php expert with enough linux knowledge to get what I need done. I am not a linux expert but have worked with it for over a dozen years, and understand configuration for mysql, apache, bind, postfix, etc. We need someone that is a specialist with these things, most specifically mysql, and that clearly has more knowledge than I have. The "linux experts" with our hosting company are far from experts and I have more knowledge than them for these specific issues. We have hired them a couple times in the past and they have proved their incompetence, and we are not looking for someone that is on the same level as they are, we need a specialist. For your bid, including a brief description of something you would do to let me know that you are competent would greatly increase your chances of being rewarded the project. I don't need you to say what fixes you would do, but to say enough to let me know you understand the issue, have worked on projects like this, and that you are competent enough to solve our problems or advice us what we need to do so our server operates smoothly.