Translation:We have four old trees in our garden.
why "in OUR garden", when in czeh sentences you haven't any words such "NAŠÍ"?
Because English loves this kind of specification and Czech does not.
Udělám to levou rukou. / I will do it with my left hand.
From the context, I am assuming that zahrada means garden as the British use the term. Americans would only have flowers or vegetables in their gardens. Old trees would be in their “yards.”