Hi there
We are sorry to hear that the Application is crashing after 10-20 sec of opening.
Is this a behavior with a particular PDF file or with all the PDFs you try to open? Please try with a different file and check.
Is the file located locally on your computer or is it on a shared network/drive? Please try to download the file to your computer and try to open with Acrobat Pro XI and check.
What is the exact version of the application you are using? To check the version go to Help > About Adobe Acrobat XI
Adobe Acrobat Xi is an old and end of life application and no longer supported. The last version was released on 14th Nov 2017 version 11.0.23. Makse sure you have the application updated. go to Help > Check for Updates.
You may also download the patch manually from the link Overview — Release Notes for Legacy Acrobat Products
You may also refer to the help page End of support for Adobe Acrobat XI and Reader XI for more information.
Regards
Amal