If your vocabulary and grammar are good, then there should be no obstacle for building sentences in Gerana. Maybe it's a unconscious dear of making mistakes that's blocking you.
Just try to start with very simple sentences using the present tense.
Das Haus ist groß.
Then, try to add subclauses to it
Das Haus, in dem ich wohne, ist groß.
Let the next sentences start with a pronoun.
Es hat einen Garten.
Add a slightly more complicated sentence using the passive verb form in a past tense.
Es wurde 1984 gebaut.
Add something to it.
Es wurde 1984 von meinen Eltern gebaut.
In short, start with simple sentences and try to make them a little more sophisticated in a second round.