I tried to write something in Psat, present, future and conditional.please check.

[Firstuser]

This weekend I have been in a congress in Madrid.
Last Friday, I went to the hospital at 8:30h in the morning. I visited some patients and I
finished the work at 12:30h at might day. Then, I went to the airport and I took one flight
destination to Madrid. The plane took of one hour late. I arrived at Madrid at 16:00h.
One taxi driver picked-up us and carried us to the hotel where the congress was held.
The hotel was a big black building made with crystal, thirty floors high.The meeting started at 17:00h in the evening. Every each fifteen minutes, one speaker talked about one item related to Multiple Sclerosis. All the lectures were interesting.The main purpose of the congress was to actualise and explain the most important concepts and news that were communicated at ECTRIMS some weeks ago.The meeting joined more than one hundred people. We gather in order to talk about MS and to sum up the most important new concepts of MS. The lessons finished at 20:30h. One hour later, we met all together at the 30th floor of the hotel to have dinner. We ate pasta and meat. And we drank wine and water.After the dinner we went to sleep. Everybody was tired because everybody had been working during Friday mornig.The meeting continued on Saturday morning and finished on Saturday evening.For came back to home, I took the train Madrid-Tarragona.I usually prefer travel by train instead of plane. So, I use to travel by train for work and for holidays.To sum up, last weekend I had been in Madrid, but actually I had not visited anything of the city because we had been inside the hotel all time
§If I go to the cinema on Monday and Friday, I will have gone twice at cinema this week.
§ If children go to school, they will learn new things and they will improve their knowledge.
§ If I eat more fat food than now, maybe I will increase my weight.
§ If I had gone at that meeting, I would have known your friend.
§ If I take the metro, it could be cheaper than if I take a taxi.
§If he shows me the software and how the program works, I will work with this computer.
§ If you pick-up me from home at 9:00h, we will have enough time to arrive on time at train station.
§ She has an exam tomorrow. If she had studied yesterday, now she could go to see the concert, but due to she had not studied anything, now she has to study.
§ The winter has arrived. If I had taken my coat, now I do not have cold.
§ If you had come with me at Barcelona, you had visited the Sagrada Familia church.
What do you think about travel by balloon?
I think that it could be exciting and surprising. Since some years ago, I try to convince
my friends for do a trip by balloon. Probably we will go next spring, when the weather
will be better. Next April, a balloon meeting will be organized in Igualada. We could take benefit of this meeting and we could travel by balloon.Next Thursday, a new play is going to start at Coliseum Theatre. My friend and I are going to see this play.Next Monday at this time I will be working at hospital. What will you do next Monday? I will go to the concert whether you came with me. If you do not came, I will not go.There are many clouds, maybe it will rain in few hours. Do you think that is it going to rain?
My chief ask me about my project. I answer that the project will be written next week.
Next weekend will be the birthday of my friend Carlota. Probably we will organise a surprising dinner for her. And obviously we will sing the birthday song and she will blowout the candles.

[E2e4]

Firstuser, I hope you don't mind my try.

[Beeesneees]

I got as far as your first sentence's correction E2e4. The original was better as there were no grammatical errors. 'Having been held' is the wrong tense for this sentence.
_________________
Cheers m' dears!

[Firstuser]

thank u very much. I did a lot of mistakes. I have a question:
What about `since some years ago´ that I used in last paragraph. Is this correct? Shouldn´t be `for years or for many years´?

[E2e4]

1. Since some years ago, I have been trying to convince my friends to do a trip by balloon.

"Since" together with the present perfect continuous here means "from then to now".
"For" wouldn't match "ago".

2. For some years, I have been trying to convince my friends to do a trip by balloon.
For some years means here "during this period of time".
Anyway, the meaning of either #1 or #2 is the same for me. Thanks

[E2e4]

This weekend I have participated in a congress having been held in Madrid.

BN, which tense would you use instead of the perfected past participle, passive voice?
"which was held" ?, or just use an ellipses as it had been written before I "corrected" it?

In addition, please let me know can I also use "as it was written before I corrected it" in my sentence I wrote before this one?

Thank you

[Firstuser]

[E2e4]

[Beeesneees]

[Beeesneees]

[Beeesneees]

[E2e4]

[Beeesneees]

That's okay too.
_________________
Cheers m' dears!