Fix up and Straighten up

Fix up verb - Make arrangements for.

Straighten up and fix up are semantically related In some cases you can use "Straighten up" instead a verb "Fix up".

Straighten up verb - Straighten oneself.

Fix up and straighten up are semantically related in tidy topic. Sometimes you can use "Fix up" instead a verb "Straighten up", if it concerns topics such as correct a situation, make neat and orderly.