Hi Pratham! Bootstrap is already implemented in Mendix as it's part of the Atlas UI!
Actually, updating bootstrap or installing a new bootstrap besides it might conflict with Mendix and I would not recommend it.
Best to use the implementation that is already provided for you!
1. Type bootstrap in the app explorer.
2. Find Atlas_Core in App > Marketplace module > Atlas_Core.
3. Open the _bootstrap.scss.
4. you see the bootstrap version * Bootstrap v3.3.4.
Mendix is operating on Bootstrap. Not the latest version, though (even Mendix 10.2.0 uses Bootstrap v3.3.4). It can be confusing if you already know Bootstrap 5 tricks, but they simply won’t work.