The Autumn

It is many a long time (or it's been a long time) that I don´t write since I have written here but it helped me a lot the times I wrote on this notebook during the summer we have just said good-bye to. During this mute quiet(??) time many things have been changing not only in the world or in my personal life but also in the landscape. The trees I see through my window have progressively turned into yellow, brown and even red colours. Besides, my chrysanthemums are spectacular. What amazing nature!

Very good! My corrections are in red and my suggestions to sound more natural are in blue/grey.

"during the summer we have just said good-bye to" - This is how you will hear many people say it, even though you may have learned not to finish a sentence with a preposition ("to").

Another way to say it would be "during the summer to which we have just said good-bye". This is probably more correct but less common!