>Does somebody know some site where I can find tests and tasks for Visual Fox Pro so I can practice programming?

There may be [at least] two kinds of programming:
Full Cycle Systems Development - And Maintenance. Full cycle development more or less requires the programmer to learn the requirements through a combination of either interviewing the end user and or reverse engineering and existing solution. When I started my career, my employer sent me to a nine month flow charting course. It went from a simple start stop flow charts to big (really big!) full systems charts. We did not write any computer code - we just drew structured flow charts on the back of wide perfed green bar or meat wrapping paper. I found a site that offers free harting tutorials.
http://home.att.net/~dexter.a.hansen/flowchart/flowchart.htm

The book recommended by Cindy (using VFP 6 by Bazian (special edition)) is a great book (especially if you you want to learn how VFP can integrate with Word or Excel). Bazian has some great little projects that will help you develop a micro understanding of VFP, OOP, VBA and others.

There is also the Tasmanian Trader that is packaged with VFP. You can also download some projects from this site. Adapt them to your needs, or stay up late and make them better(!). Learn ActiveX.

But the best way [to learn] is a small project that your work associates (or family) might be able to use. The goal is to develop something that non-programmers can use and trust. IF that is accomplished everything else will follow!

Good luck - and remember - practice, practice, paractice :0)