Hello,
Thanks for reaching out! I'm Microsoft user like you.
I can understand you are facing issues with some files types being changed to .pdf.
Click Start button -> Open Settings and
Click on Apps settings.
On the left side, you will see Default apps. Click on it.
Scroll down –> Click Reset to Microsoft recommended defaults.
Click on the Reset button and all your File Type Associations will be set to their original values
Reboot your computer.
In case of additional questions, reach out back to me, and I will be happy to help and try our best to resolve your issue.
Best Regards,
Prakash