"To stay in my house" is the translation for that.
Usually it is used in a sentence, like
Quiero quedarme en mi casa
(I want to stay in my house)
Mi mamá me dijo que tengo que quedarme en mi casa.
(My mom told me that I have to stay in my house.)
¿Puedo quedarme en casa?
Nothing, I'm at home.
En la casa (at the house) En casa (at home)
Answer: Quedate en casa
If you are saying what you are going to do is "Ir al cine el Sábado, y quedarme en (mi) casa el Domingo" (infinitive) If you are saying this to another person as an order or suggestion "Ve al cine el Sábado y quédate en (tu) casa el Domingo" (imperative/subjunctive)
Ayudar en casa = to help at home. There is no Spanish word "Ayundar"
I am at home resting
Ella vive independiente, en su casa.
in your house or in your homme
in the house
"cuántos cuartos hay en la casa?" means "How many rooms are there in the house" in English.
Yo vivo en una casaVivo en una casa. Vivo en una casa.