Simplify the following text for a Grade 5 native English-speaking person.
Original: His intention was to attach a few helium-filled weather balloons to his lawnchair , cut the anchor , and then float above his backyard at a height of about 30 f for several hours .
Simplified: He planned to attach a few large balloons filled with helium to his lawnchair and then float above his backyard . He planned to stay about 30 feet up in the air for several hours .