With Covid, you should be able to take an online language class where online classes were not offered in the past.
You can be in and take a class at your community college at the same time you are in HS — “concurrent enrollment”.
For example, you could take level 2 at CC fall quarter, level 3 at CC winter quarter. Assuming you can take a placement teat in your heritage language that allows you to skip level 1.
You don’t have to have the class completed before submitting your application. However, I agree with another poster the summer after graduation will likely not be accepted. So it should be planned to complete before graduation.