Create/Modify a MySQL Event to Update Table Nightly As Efficiently As Possible - Strong Math Skills Required

I have a MySQL table that contains cumulative stats for users. Each night these stats need to be updated with data from various tables in the database. I created an event that recalculates the stats each night, but this takes a lot of time to do. Basically the event I create empties the destination table and completely recalculates the columns. This is inefficient method of doing this. I need an event to be written that will update the table with new data. For Example: User1 has 400 wins. Each night the current MySQL Event Counts() each win for this user. With over 2mil records and over 100k users this will take a long time. Instead, the event could look at just new wins since last event was run and add the new wins to the record. This is repeated for each column in the destination table. I need someone very strong with writing MySQL queries and who is strong in math/statistics since the destination table is a table of statistical records. Each field in the destination table needs to be calculated with the least load on the server and as quickly as possible to achieve the correct values. Attached you will find a sample database (zip) and the current nightly event being used to make those calculations. The freelancer who can demonstrate he has the skills to achieve this at the least cost and fastest project completion will be awarded.