Perhaps silly q; how do I get a more secure lock fitted to an older styles doors?

[Themeparknetherland]

So it's a wooden door,how would I upgrade it to a more secure lock without buying a whole new door?

You can just buy whatever locking mechanisms you’d prefer (Yale or deadlock for example) then have them fitted. A handy man should be able to do the job, a lock smith would charge a fortune. DH could manage it but it isn’t something I could do myself although there are video tutorials on YouTube if you fancy giving it a go. Drills terrify me and I’d likely drill/chisel too much wood out and need a whole new door!

Just examples, B&Q & even Amazon sell Yale and deadlocks.
www.screwfix.com/p/smith-locke-traditional-rim-deadlock-black-105-x-80mm/7041G?tc=KC6&ds_kid=92700058168038603&ds_rl=1244072&gclid=CjwKCAjw9NeXBhAMEiwAbaY4lnLR97tIkXAzyduoFERIb0rJ0ViPeYuskr2wxSg6iTiMQZLNkgkweBoCjRwQAvD_BwE&gclsrc=aw.ds

www.screwfix.com/p/yale-77-traditional-night-latch-polished-chrome-plated-60mm-backset/78737