Hello. I can help you, but I can't see the lesson section page 3. I'm Cuban and a Spanish teacher. So, if you give me more details, I can definitely help you.
Hay sillas delante de los ordenadores.
Halla: el significado de halla corresponde al verbo hallar o encontrar.
Haya: 1ª o 3ª persona del singular del verbo haber.