@Franky3Goldman
Sorry you either need to upgrade your Mac to a newer OS or get or borrow a newer Mac or use a WIndows computer. Or you can use the Online internet version this year. If you can't run Turbo Tax you can get a refund. https://support.turbotax.intuit.com/forms/refund-request.jsp
If you need to switch to the Online version you can transfer from 2019 into the Online version. If you used the Desktop program last year here's how to transfer into the Online version, expand the blue link if you used the CD/download last year. You will need to have the filed ending in .tax2019 on your computer. Transferring from last year will clear out anything you have entered for 2020 and you will have to start over.
https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-...
If you used the Desktop program before you may not like the online version. It has less features and no Forms Mode. You can only do 1 return. Your return is only saved online so be sure to save both the .tax2020 data file and the pdf file to your computer when you are done. In case you need to amend it in the future or if you need a copy to get a loan or something. You might not be able to access your online return when you need a copy.
Mac System Requirements. For 2020 you will need macOS Mojave 10.14 or later
https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-...
Online system requirements
https://ttlc.intuit.com/community/system-requirements/help/turbotax-online-system-requirements/00/25...
