Can you show a picture of the tail, that is how to tell if its a male or female. That size can be almost full grown for a male.
Also this is the best place to start: https://tortoiseforum.org/threads/info-for-new-people-please-read-this-first.202363/#post-2036954
its a lot and very dense, so please ask questions.
Also since you are in the UK: There is an app called TortTable (desktop version: https://www.thetortoisetable.org.uk/) which lets you look up good foods
There are quite a number of UK members on here who can also offer more localized advice