You need to get the floor perfectly clean to start.

A few key holes to help the new surface lock in may be good.

You want to do it in sections. Leave the middle hump until last
(thinnest section)

There are newer patching materials for concrete that can go to 1/2"
with no problems but surface preparation is essential.

The cheapest method if you can do the work is to chip out the hump.

Note: If the slab has a foundation at the edges you do NOT want to
break up the slab.

Consult a concrete worker in your area,