Could you please check the following sentences, please?

1) He kept himself busy by keeping (?) record of how long he had been on the island.He made a mark for each day he had been on the island.
2) He decided to build himself a house in a cave. He found a cave halfway up the hill, which was comfortable and dry. He sorrounded it with a fence consisting of sharp wooden posts (?).
3) The cannibals landed twice on Robinson's island.
4) My parents are always critical of me. They always get at me.
5) I felt ashamed when the teacher gave me my test back.

1 - For word-choice variety, you should probably use "stayed busy" rather than "kept himself busy." Space after the period.

2 - surrounded

4 - "get at" = what??

5 - delete "me" - it's repetitious