You have two excellent options here for web development in Python:
Both of these packages work nicely with several different GCP products. Personally, I prefer Django because it provides a more comprehensive workflow, but it has a steep learning curve. Flask, on the other hand, is much more lightweight and works well for small projects. Both options provide nice templating that is suitable for the type of website you are hoping to develop.
Regarding your infrastructure, a lot will depend on how involved you want to get. If you wish to develop websites and host them on GCP, you can look at the many different options you have available to you.
The two primary services for dynamic websites are Cloud Run and App Engine. If you want to focus on mobile development, you can have a look at Firebase Hosting. Although it is possible to use Python and Firebase to integrate your website with a mobile option, the most popular method seems to be using Flutter/Dart.
An excellent place to start is to play with some of the available products. There is a Cloud Run interactive walk-through to get you started and some good Python documentation for App Engine. If you want to create a Python-specific development environment with GCP, it is good to follow this guide to help you get started