Sure! Here are the rewritten sentences:

1. My favorite hobby is collecting stamps.
gI love **to collect stamps**.

2. We find organizing an English festival in our school interesting.
gWe think **that organizing an English festival in our school is interesting**.

3. I spent two hours doing the gardening at the weekend.
gIt took **me two hours to do the gardening at the weekend**.

4. The Japanese work hard and they do exercise regularly, too.
gThe Japanese **work hard and also exercise regularly**.