I’ve had my phone for a week and already have had to uninstall and reinstall several of my favourite, most frequently used apps.
My home security alarm doesn’t work at all!
That’s not really much information to help you!
Which apps are crashing?
How do they crash, just closing or shutting down with an error message?
Were the apps and their settings imported from another device?
On which OS (version) is your device?
…
Welcome to the community and the forum 
Uninstalling / reinstalling is not generally necessary. All that does is to delete the data associated with the app, either regular app data or cached data.
You can achieve the same much more quickly by deleting the cache data and, if really necessary, the user data. To do that, go to
Settings > Apps > All apps > [tap the app] > Storage and cache
To begin with, choose “Clear cache”. This will put many things right.
If necessary, choose “Clear storage”, which is the equivalent of reinstalling the app.
To report your OS version, as suggested by mike_1312, go to
Settings > About phone > Build number, and report the value of that parameter.
The apps were transferred from a pixel 6a phone. I’ve realized though that I have needed to uninstall and then reinstall most apps on my fairphone 6. The one’s still proving difficult to get to consistently open are Bible Project and Home Control app for Pyronix security alarm
This could be the problem. If you read around this forum, there are several topics having the same problem like you, that’s why I asked you all the questions.
It seems like that when you transferred your apps and settings from the old device to the your current FP6, the settings do not align with the hard- and software of your new device.
Google is lying when they tell you, that you can transfer your apps, data and setting from one to another phe without any issues.
Like @OldRoutard already mentioned, the best would be to delete cache and storage of the problem apps and set them up from the scratch again.