My sidewalk isn't level. Can I patch it?

Easiest way is to call a guy that does concrete work, he breaks up the flag, puts in forms and lays new concrete. Patching won't last and will eventually cause a tripping hazard on its own. A 5 x 5 flag is 1/3 yard of ready mix. The job is about $150.

In the old days, you would just put boards on either side [making a mold], and then pour in mixed concrete. You can get a bag of cement powder, mix with water in a wheelbarrow and poor it on.

If you want to do it perfect, the contractors will jackhammer up the old sidewalk, put molds down on the side and poor a new sidewalk.

Topping the corner/edge with concrete won't work. It won't be thick enough for strength; especially as it feathers out into the middle of the slab.

No, you can try using a 6' (foot) crow bar and levering it up so you can stuff some sand underneath the offending corner/edge. Make it slightly higher than the next slab for settling.

Minimum slab over with fiber mesh concrete is 2 inches. If your trip zone is at least 2 inches or more you can do a form and slab over with the correct concrete.

It sounds like tree roots. If that's the case....it gets complicated and expensive.

Good luck!

break the whole section with a sledge hammer (goggles a must) use a wheel barrow mix 4 bags of sackreet cement mix. level with a board. brush with broom. allow to dry. then rewet to season it better

Just walk crooked.