You may take a second project while working on another project if the following conditions are met:  

• Your translator level must be Gold or higher to take a small project (<600 words) in addition to a big one (>2000 words).
• Your translator level must be Silver or higher to take a big project (<5000 words) in addition to an ongoing small one (<200 words).
• Both projects must be delivered on time. 

Note: these conditions apply to exclusive projects as well.

To find out your level, go to Control Panel and open the Performance board:

If the above conditions are not met, you will see the following error message: