Could you correct my small post? Many thanks in advance for your help.

How are thing going there? I hope you have been enjoying summer and have been having amazing summer months. I do hope this letter finds you and your family in a good health and happy.
Sorry for not writing sooner, but I have a good excuse- I have been away where there is no internet connection and I couldn't use the internet for more than two months.
This is the first year I could afford to go on a holiday. My daughter has always dreamed of swimming in the sea and I decided to fulfill her dream. We stayed in a holiday resort in Lazerovaskoe ( district in Sochi) and had a fabulous time there.
Unfortunately, a holiday in Russia is very costly and I had to take a loan from the bank.
My holiday went well but sadly two weeks before our departure to Sochi my husband shocked me by saying that he is leaving me as he fell in love with another woman.
We went to Sochi by train which was new and was constructed speacially for the Olympic Games. It had two floors, there was air conditioning, and the train was very clean.
As for the sea, it was very clean and you could see even small fish of every color at the bottom of the sea.
However, many inhabitants said that after Olympic Games there have been very few fish for the fishermen to catch.
We returned by plane because one of the trains derailed and we had to go to the airport by taxi as there were no trains to the airport.
On Friday I went to work the first time after my holiday. I did only menial work- washed two windows and was removing stuck bubble gum from the floor in the chemistry class.
Summer will soon pass and it will be cold again.
I must go now.I hope to get good news from you.
Your friend Lada.

Could you correct my small post? Many thanks in advance for your help.

How are you donig? I hope everything is well with your family? I hope you have been enjoying summer and had amazing summer moths. I hope this letter finds you and your family in a good health and happy.
Sorry for not writing sooner, but I have a good excuse- I had been away where there is no internet connection and I didn't use the internet more than two months.
This is the first year I afforded to go on a holiday. My daughter dreamed of swimming in the sea and I decided to fulfill her dream. We stayed in a holiday resort in Lazerovaskoe ( district of Sochi) and had a fabulous time there.
Unfortunately, holidaying in Russia is very costly and I had to take a loan from the bank.
My holiday went well but sadly two week before our departure to Sochi my husband shocked me by saying that he is leaving me as he fell in love with another woman.
We went to Sochi by train which was new and was constructed speacially for Olympic Games. It was two floored and there was an air conditioning and the train was very clean.
As for sea it was very clean and you can see even small fishes of every hue at the bottom of the sea.
However, many inhabitants said that after Olympic Games there are very few fishes to catch for fishermen.
We returned by plane as one of train derailed and we had to go to the airport by taxi as there were no trains to the airport.
On Friday I went to work the first time after my holiday. I did only menial work- washed two windows and was removing stuck bubble gums from the floor in the chemistry class.
Summer soon will go and again we will have cold days. ))
I must go now.I hope to get good news from you.
Yours friend Lada.

Could you correct my small post? Many thanks in advance for your help.

How are thing going there? I hope all is well with your family. I hope you have been enjoying the summer and have been having amazing summer moths. I do hope this letter finds you and your family happy and in a good health and happy.
Sorry for not writing sooner, but I have a good excuse- I had been away somewhere where there is no internet connection, and I hadn't used the internet for more than two months.
This is the first year I could afforded to go on a holiday. My daughter dreamed of swimming in the sea, and I decided to fulfill her dream. We stayed in a holiday resort in Lazerovaskoe (the district where Sochi is located), and had a fabulous time there.
Unfortunately, holidaying in Russia is very costly, and I had to take out a loan from the bank. [variant:  and I had to take out a bank loan.]
My holiday went well, but sadly, two week before our departure to Sochi, my husband shocked me by saying that he was leaving me, as he had fallen in love with another woman.
We went to Sochi in a train which was new, and was constructed specially for the Olympic Games. It had two levels, and there was an air conditioning, and the train was very clean.
As for the sea, it was very clean, and you could see even small fishes of every hue at the bottom of the sea.
However, many inhabitants said that after the Olympic Games, there were very few fishes left for the fishermen to catch.
We returned by plane, as one of trains derailed, and we had to go to the airport by taxi, as there were no trains to the airport.
On Friday, I went to work the first time after my holiday. I did only menial work- I washed two windows, and was removed stuck bubble gum which was stuck to the floor in the chemistry classroom.
Summer soon will be over, and again we will have cold days. ))
I must go now. I hope to get good news from you.
Yours friend, Lada.

Very good.

I recommend that you look for a webpage that can teach you how to properly use commas in English.

Here's one rule:   When a coordinating conjunction (and, but, or, nor, for, yet, so) joins two independent clauses, place a comma before the coordinating conjunction.