I am new to gardening and therefore to this website

Not a website! It's a newsgroup, which you are reading via a website.
Most of us are reading it via newsreader software, which lays out all
the threads in an easier-to-follow fashion.

and we have
recently moved into house with huge garden and we are feeling quite
overwhelmed but love it (sort of). We are trying to keep a diary of
what we are doing and trying to learn the names of all our plants.

I wondered whether anyone can tell me what type of shrub we have in our
garden - it has green fruit, the size of a large walnut that turn
yellow
later in the year. Does anyone know what it is?

As others have said, there's a good chance it's a japanese quince or
chaenomeles. Slightly leathery green oval leaves about an inch long.
Abundant 5-petalled flowers in spring in any shade from pale pink to
brilliant orange or red.
--
Kay