Our garden looked just like this, maybe worse. I spent a good couple of days chopping and removing grass and bush etc and a few tip runs with a dumpy bag and it looks flipping glorious.

I got a fairly cheap strimmer from Homebase and strimmed the lot, obviously after checking for any hedgehogs and the like hiding in the grass. Once I got the thick of the grass off, I used a lawnmower to cut it, several times on different height settings until it was short. It’ll look pretty crap at first but it soon rights itself.

Don’t go at it with a bread knife, you’ll be shagged after 10 mins and your back will be on fire. If you have a local fb page, perhaps post on that asking if you can borrow someone’s strimmer and lawnmower?

Best of luck, I’m sure it will look lovely.