Most bike shops in Groningen also do repairs, so have a look at one of the bike shops in your neighbourhood. Many bike shops also offer replacement bikes for the time it takes to repair your bike.
One of the most used ways to buy second-hand furniture is Marktplaats. If you do not like online shopping, there are a couple second-hand shops in Groningen. One of the biggest ones is Mamamini, where you can find a lot of second-hand furniture. City Central also offers a Vintage Furniture tour.
You can read more about recycling in Groningen on the waste guide ("afvalwijzer"). If you want to recycle your old paper, there are often old paper bins nearby and old paper is collected once a month. You can recycle glass by putting it in the glass bins. Make sure to check if it is glass with a deposit ("statiegeld"). Many supermarkets have bins for batteries and light bulbs if you are looking to recycle those.