There should be a default app called "App Store" on your phone with an icon that looks like a black and white 3d cube. Open that, and you should see the option to install Google Play Services.
After you've installed Google Play Services, I recommend installing apps through Aurora Store, as doing so doesn't require you to link your device profile to a Google account (which is better for privacy).
If apps still crash upon opening, open Settings, then click the tab that says "Apps". Once you've done that, select the app you're having issues with through the interface, then scroll down and enable "Compatibility mode" under the "Exploit Protection" subheading.
I hope this helps!
Note: If you want to improve your online privacy and security, I'd recommend switching email providers to one that's more privacy respecting, like Tuta or Proton.
I'd also like to note that just because police can't access your phone, it doesn't mean that they can't find information through other means, such as social media.