1. ¿Llamaste a tu amigo ayer? 2. ¿Lo llamabas con frecuencia?
3. ¿Fue la madre de tu amigo quien contestó el teléfono ayer?
4. ¿Contestaba su madre casi siempre?

The first one means, "You called your friend yesterday?"

The second one means, "You called him frequently?"

The third one means, "Was it your friend's mother who answered the phone yesterday?"

The fourth one means, "Her mother answered almost always?

Explanation:

I hope this helped.