Here is the problem:
It is very easy to fix this.
You will need:
- a spanner or a pipe wrench
- peace of fabric
- glass
- vinegar (9% is great)
So first, you have to undo this mesh on the end of the tap. As you see it is full of limescale.
If you have spanner, find the right size (in my case it is 22 mm) and undo it. Grab the tap with one hand and undo the mesh with spanner in the other. (I only use one hand for photography reasons)
If you don't have spanner, you also can do it with pipe wrench. In this case, you should wrap a piece of fabric around the mesh and then grab it with wrench.
Here it is. Full of limescale end sand.
Now take the glass, fill it with vinegar and put mesh and all the stuff it came out with in it. Leave it to sit over night.
Other day:
All you have to do now is to put all together and enjoy in nice stream of water :)