Hi @Kaan ,
It looks like you’ll have to rush things a bit now, but if (like I did) you use what it’s now called Bundled Services ; then, you’re migration to Python 3 could be done a lot faster (unless you use third-party libraries that need to migrate as well).
Most of my time during this upgrade I spent it migrating webapp2 to Flask, which meant migrating also Django templates to Jinja2.
These should help:
https://www.youtube.com/watch?v=Tyyv4_Khyk0&t=271s
You’ll find in the description many other useful links.
https://codelabs.developers.google.com/codelabs/cloud-gae-python-migrate-1-flask
https://github.com/GoogleCloudPlatform/appengine-python-standard
Also, just ask here if/when you get stuck and most of the time you’ll get help.
Best,
Michael