Newbie gardener looking for advice

Hello all, I’ve lived in a flat most of my adult life so never had a garden to look after. We’ve just moved into a new house with a large garden and a lot of things growing. My little boy loves having grass to run around on so that is fantastic but the outer borders are quite full on and overwhelming.

I have no idea whether the previous owner was a master gardener and has created something beautiful or if this is just an overgrown mess with the worst kind of shrubs going.

Does anyone have any advice on how to get started maintaining this and if there is anything you can see that needs more urgent attention?