You hit something when you connect with it, hard. Some examples are hitting a nail with a hammer, hitting a ball with a bat or hitting a target with an arrow.
Something lands when it comes down from flying in the air and alights on the ground, or on water or similar. When you land, it is called a landing, for example "Look at the pilot landing her plane".
You limp when you walk unevenly, so you keep your weight off a sore leg or foot. When people or animals limp they tend to move very slowly and unevenly. Another word for limp might be hobble.
Limp can also mean something that is soft and floppy.
Marching is a way of walking that is brisk and formal. Soldiers march together with their steps in time with each other.
See also: March, the calendar month.