Can you all help me, finding the best growing conditions for a Chinese elm

-Bonsai stands 'inside' That was my first mistake , that I learned on this forum.
-Watering ( when is the soil dry or moist? ) read about over watering etc.
-fertiliser
-Temperature

I live in the Netherlands , so winter/autumn this week Temperature variate between -1 to 7 degrees Celsius , with clouds and poor light.

Any time used for replying , is already welcome and I thank them.

Hey, welcome.
You are correct Chinese Elm is a hardy species and is best kept outside if you want it to live long. There is no such thing as over watering just watering too often. Use a chopstick to test when the soil is dry, if it comes out clean then water thoroughly. Little and often is not good.
At this time of year no fertiliser as the tree is not growing, add fertiliser during the growing season every 2 weeks if liquid. I use a slow release so only every 6 weeks I add more. Change to low nitrogen in August, then stop in October, depending on the weather. Have a look at bonsai4me.com for more species information.
You can PM me if you want more information,
Geoff.