Hello MimiDima,
Thank you for using Apple Support Communities. It's my understanding the Quickbooks app has been crashing on your Mac. I know I would be concerned if I was unable to use an important app. I am happy to help.
Here are a few steps to try to get this issue resolved.
Restart your Mac.
Read the app’s documentation to check if it’s compatible with your version of OS X.
Open another file in the app. There may be a problem with the original file.
Check for updates to your software.
Disconnect any peripheral devices you just connected (for example, a printer). They may not be compatible with your version of OS X.
Uninstall any app plug-ins or enhancements from other manufacturers.
If you recently updated the app or OS X, a plug-in or enhancement you installed may no longer be compatible.
Use Apple Diagnostics or Apple Hardware Test. These tools can tell you if hardware you installed, such as additional memory, is incompatible, improperly installed, or defective.
Restart your Mac in safe mode.
OS X El Capitan: If an app freezes or quits unexpectedly
Have a wonderful day!