Preview saves pdf files as jpeg instead of original file forma since update big sur 11.2. How to fix this?

When I open a pdf file from a received email and then save this file to my harddisk, it save the file not as the original file extension (.pdf) but as a jpeg image, losing all other pages of the pdf file. I want to save received files like they are in the format I received them by default. A function I use daily and don't want to use a less efficient workaround. Why did this change and more importantly how can I fix this?

Thank you for your help.