Keep (something) straight (in one's mind/head) phrase
To be capable of understanding something completely, clearly, or precisely.
You should present your idea more clearly so that everyone can keep it straight in their mind.
She found it hard to keep yesterday lesson straight in her head.
To be able to differentiate one thing from another.
Can you figure out how to keep these two paintings straight? They look the same to me.
The verb "keep" should be conjugated according to its tense.
Manage to earn enough money to buy food and other essential things
She works two jobs at the same time in order to keep the wolf from the door.