Hello
I used some previously used chargers and cables, but some I didn’t feel so comfortable with as they heated quite a lot (even with slow charging). So I would definitely advise to get a good quality charger and a cable.
There is a growing market for accessories, you can find separate threads on this forum dicussing that.
I am happy with my 5G, no issues whatsover, but some people experiencing reboots, and the fix to that is expected at the end of this year. It is generally advisable to replace a simcard if it is more than two years old.
Not sure where you are based but perhaps there is a local store or a fairphone angel, or someone on 3network sim to give you some relevant advice.
Best of luck