It's a beautiful plant (do you have the pretty variegated version?) but will always be much happier outside - getting as much hot sun as you can give it (which is not the same as filtered sunlight through a glass window). 20C is quite cool, but it will be OK for a while at that temperature. It will need quite a large pot (it can get fairly large, so needs a bit of spreading room). It will survive outside at 15C, but won't do much growing.

To make an infusion (tea), pour 1 cup boiling water over 1 teaspoon fresh or dried leaves. Use as a gargle or mouthwash or take 1-2 cups per day, hot or warm or use as a footbath for nail fungus or tinea. Or add 6 sprigs thyme to 1 1/2 cups brandy and leave for 5 days, shaking daily. Take a little several times daily when you feel a cold coming on. Tincture: Take 2-4ml three times per day.

Warning: It is safe to use thyme as a seasoning during pregnancy but strong medicinal doses should be avoided if there is any possibility that you are pregnant.

Reminder: ALL herbal teas are medicines in the same way that conventional medicines have an action (or several actions) on the body - some wanted, some not.

Many thanks for your reply! It was very quick!
What do you mean by "do you have the pretty variegated version?"

And I wanted to know if my little bush of Thymus needed to be cutted sometimes and how much water should I give to the plant?

If you're using your plant, then your cutting (pruning, harvesting) it. Just don't remove more than one-third of total growth at any one time, and allow the plant to regenerate before you do it again.

As for watering, although the books will tell you that thyme prefers a dry soil, don't you believe it! It can take plenty of water, but that water MUST be allowed to drain away quickly. No sitting a pot in a saucer of water, thank you! That will kill it quicker than blink.

Never allow potting mix to dry out completely. That will result in a soil which becomes water-repellent. The water will flow down the sides of the pot, leaving the poor roots in desert conditions. To test whether your plant needs watering, use the Finger Test. Poke your finger into the soil as far as it will go. If the tip of your finger emerges dry, give the plant a drink. If the tip of your finger feels cool and moist, water the plant later.

Since you're growing your plant indoors, the best way to do the watering is to take it outside, give the plant a drink, allow the excess water to drain away naturally, then bring the pot back inside - THEN put it onto a saucer to catch any further drips. This is one of the biggest problems with indoor plants - drainage!

Also, your plant will really benefit from exposure to outside sunlight from time to time - every day if you can manage it. Thyme just LOVES the sun and is happiest with the full blast of the sun on it for 6-8 hours a day or more (once it's mature, of course - baby plants need to be gradually exposed to more and more sun).