Are there any errors?  (you are almost fluent!  here are some suggestions:)

Hi guys, are there any errors in this postcard? Thank you.

Dear John,
what are you doing? I'm in London and I'm having a fantastic time here. I arrived three days ago and I'll be staying here for about four days. I'm residing in a college with other students from the rest of Italy. I'll be studying English in London for a week with an eEnglish teacher. Her name's Apostolia and she come from Cyprus. She's about thirty years old and she's very nice and funny. She has explained the english future future tense in English to us recently (Is correct? Can I use the present perfect?). She'll be accompanying us to visit London city. Then, in the afternoon, we're going (Can I use the present continuous?good) into London eye to see the city from above. At 5 o'clock we're returning to the college (Again, Can I use the present continuous?yes). At 6 o'clock we have dinner. In the evening we usually go out for a trip. Tonight we'll be watching an english film. At the moment I'm having fish and chips, it's fantastic! And what about you? Did you have a dinner?

See you soon.

Nice job!!  here are a few suggestions:

Writing Practice

A: Have you changed your mind about the destination for your next vacation?
B: Why should have I changed change my mind? I think Australia is a quite interesting place to visit. Don't you think so?
A: Sure it is, that's not my point. It's just that Australia is very far from here. I believe it's kind of 20 hours or something like that. You told me that you planned one-week holiday and I suppose the flight isn't cheap. That's why I was wondering thinking that you might have been having second thoughts.
B: It's not as crazy as it seems and, as matter of fact, the airfare wasn't that expensive. I got a pretty good deal on a new booking website that is trying to carve a niche in the market.
A: I can understand that but to me the time you'll be able to enjoy your vacation doesn't pay for the trip. Not to mention that you'll be right back at work when you'll be returning you return.
B: You're probably right, but it's too late now. Everything has been set. I'll be keeping a positive thinking. positive thoughts.
A: I wish that'd be enough. I hope that's enough.  Good luck!

Thanks in advance for you feedback.

tense exercise.

good a) The house was quiet and I realised that eveyone had left.
good b) It was a hot sunny day and Martin was having a picnic.
c) Immediately I walked into the room I and saw the table in front of me.
good d) I first met Maria when she was running on the street.
e) When Giuly heard Tom's voice on the phone, she knew his's had somethings something was wrong.
f) John was working at his desk when ringed the phone. when the phone rang.

My morning

In the mornig I take my daughter meeting her scout friends. They had meeting at 9, and we were late because it was 9.20 ( can I say "because we were 20 minutes late "?). There was nobody where they had to meet, so I thougth they had already gone away. I was thinking what to do when I understood : it wasn't late, it was early because last night time was changed , now there is winther time.
THANKS TO EVERYBODY WHO WANTS TO CORRECT ME

Hi Cinzia-- your English is great!  here is a suggestion to improve...

In the morning I take my daughter to meet her scout friends. We were late as it was 9:20 and they had the meeting at 9:00.  There was nobody there, so I thought they had gone.  I was thinking what to do when I understood:  it wasn't late, it was early because the time changed last night.  Now it's winter time.

Sharon

Mauro Corona. Vajont, quelli del dopo

Mauro Corona was born in Erto in 1950, a clever head gruff(not sure what you mean to say-clever, but gruff man), a sculptor and a man who tells the truth! Corona has written a book, among others, which title titled is Vajont, quelli del dopo. An interesting piéce de théâtre. He has invented (He is inventive) but not fantasized(but doesn't write fantasy) . In this book does  he mentions two realities: those who lived before and during the Vajont day and that day he lost everything: home, work, family ... even underwear; and those who arrived after the Vajont Day: to help or to make money? who knows? He lets them speak without judging. They judge each other in the dialogue , in the play, that unfortunately I hadn't see being represented , but does someone represented it? (The book begins with these words:
"Alle porte dell'autunno ua notte di tragedia era calata sulle case del paese addormentato dalle fatiche e tra le vie dove per secoli aveva pulsato il cuore della vecchia Erto. Fu come un colpo di falce. Il 9 ottobre 1963 alle 22.45 duemila persone entravano nel nulla per ambizione e interessi altrui." [...]
These opening words not only describe a tragedy that for many it is better to forget and one that we are ashamed of. It shows what Erto is today. Erto, a place destroyed in a few minutes, a whcih was place in the middle of Dolomities and destroyed from by an enosmpous  enormous wave (250mt tall). Erto: The memory of a country that no longer exists?, With people who do not live there anymore? ,with ghosts and dust? .  Or is it a country renewed by new people, by the reconstruction of a catastrophe, that is becoming a thing and now being revived with new people? (not sure what you mean here).
9.10.1963 it really happened and there still someone who can tell us the truth!

Your English is great!

you can find it on my blog silvialegge.blogspot.com and we can learn Italian discussing the topic.