Can I still file my 2020 taxes even though I filed my 2019 early this year and still have not received them back so I do not have my AGI?

[DoninGA]

Yes, you can e-file a 2020 tax return.  Enter a 0 (zero) for the 2019 AGI where asked so that you can e-file the 2020 tax return.

[fanfare]

don't wait.

You will now be filing late, unless you requested an extension of time to file your return.