[Puenktchen]

Looks like I have to wait for spring now  . Will let you know what tree it is as soon as the leaves/flowers are out 

[sunshineband]

Yes, please do 

[Puenktchen]

I found another clue which might help to identify the tree. I have looked through the pictures I have taken of my other plot which is directly adjacent to the new plot with the unknown fruit tree and in a few you can see the tree in question in the background how it looked in summer and early autumn with leaves. The pictures are not perfectly sharp as the tree was only in the background but maybe someone can say, yes it looks like a cherry, or yes it looks like an apple?

[Growster...]

The more I think cherry...;0)

[ididntdoit]

Are you sure it is a fruit tree?

[New shoot]

I'm with Growster on this one. 

The buds and bark in your first set of pictures look very like Prunus padus or Bird Cherry.  Its a very pretty tree with lovely blossom, but will have seeded in courtesy of a local bird if that's what it is 

[jaydig]

Even if it turns out to be a disappointment from the point of view of fruit, or even no fruit, just imagine a lovely summer's day, when you've been working hard on the plot, and stop for a rest and a drink - under the shade of your lovely tree.

[Puenktchen]

Thank you again. I will go for cherry tree and hope it will have some fruit in the near future. But if not I just enjoy the shade it offers in summer and the pretty flowers (also the bees will be happy) in spring. I planted two other trees, an apple  and a plum, so I will get some fruit from them at least.

[Puenktchen]

I can now reveal that the unknown fruit tree I was asking about earlier is a plum tree and I can harvest the first fruit this year. I kind of suspected once it got the leaves out that it is most likely a plum tree but it never had any fruit until now.
As to the variety, I am not sure. The fruit are quite large round plums with a greenish yellowish colour. I was waiting for them to turn purple but they only seem to change to a light yellow once ripe. They are very sweet and juicy. But the wasps like them as well so I have to be  quick.

[mumofstig]

Oullin's Golden gage  Lovely 

[Puenktchen]

Yes, Oullin's Golden gage looks exactly like my plums. Thank you! Now I know the variety as well.