но он слишком занят своими научными

но он слишком занят своими научными экспериментами и бывает дома только по воскресеньям

Результаты (английский) 1:

but he is too busy with his scientific experiments and sometimes at home only on Sundays

Результаты (английский) 2:

but he's too busy with his scientific experiments and is at home on Sundays

Результаты (английский) 3:

but he was too busy with his scientific experiments and comes home only on sundays.