Hi Frida,
welcome to the community forum!
To get answers more specific for you case, it would be very helpful to know
- which Android flavor do you use? The stock Fairphone OS (“Fairphone Android”), or /e/OS (by Murena), or another different one you installed yourself?
- which OS version are you at? Settings → About phone → Build number at the very bottom,
- in which country are you and what provider do you use?
Because there are known issues for some of the problems you describe for certain of those mentioned cases, and some got fixes recently.
“WiFi has been aweful” could be related to the DNS over TLS/IPv6 issues- Apps don't load data over Wifi - #612 by jordylicht, which just got fixed,
reboots seem to appear for some, previously also more frequently in the US/ Canada, not sure if still a thing (one, two, three, …),
etc.