Hi Michel
You have to do the following things.

1. Optimize querys in Fox. Divide you sql queries. If you consult one table the biggest with sql and a where condition to limit the scope of the answer, you get a cursor, with this cursor you can join to another tables and create a new sql consult but the speed increase a lot than if you create only one sql consult.

2. Change the process to the server side as Martin Salias advice to you in his answer to your question. (Check your server hardware.)

3. If the process continues slow try to get a local copy of the data in the computers. You can have a tool to make differential backups, in this way you only copy the data from the server once, and every day you can made a differential backup.