I left out two important things. Hopefully, you can have a look at them.

First, the sentence you asked me to vary;

1) The following items will be assessed: the pupils’ attitude towards the European Union, their disposition to mobility and their knowledge of both English and ICT.
2) I have checked everything now! From a linguistic point of view, everything was just perfect. Mainly minor mistakes due to tiredness. (Make sure to check every paragraph).
3) By the way, it would be nice if your principal could drop a few lines (in Italian) to our school's principal telling him he was glad to meet us during our preliminary meeting and demonstrating his appreciation for our mutual cooperation and efforts. Both of us have worked really hard on the project and deserve a formal congratulation (??) on behalf of our principals.
4) No one here knows about my efforts as I did almost everything by myself. As you know, I’m not going to receive any money from it! I did it for a right cause (??) and now
5) I’m really very pleased that our project will be supported by a German Member of Parliament.
Good luck with your daughter. Luckily, my son has fully recovered from the flue!Let me know if there is anything you can’t understand.

1) The following items will be assessed: the pupils’ attitudes towards the European Union, their disposition to mobility, and their knowledge of both English and ICT. This is much more clear. Good!

2) I have checked everything now! From a linguistic point of view, everything was just perfect. There were mainly minor mistakes due to tiredness. (Make sure to check every paragraph.)

3) By the way, it would be nice if your principal could drop a few lines (in Italian) to our school's principal telling him he was glad to meet everyone during our preliminary meeting and demonstrating his appreciation for our mutual cooperation and efforts. Both of us have worked really hard on the project and deserve formal congratulations on behalf of our principals.

4) No one here knows about my efforts as I did almost everything by myself. As you know, I’m not going to receive any money from it! I did it because it was the right thing to do!

5) I’m really very pleased that our project will be supported by a German Member of Parliament.

Good luck with your daughter. Luckily, my son has fully recovered from the flu! Let me know if there is anything you don’t understand.

First, let's go through the sentences you provided:

1) The following items will be assessed: the pupils’ attitude towards the European Union, their disposition to mobility and their knowledge of both English and ICT.

To answer this question, you simply need to identify what items will be assessed. In this case, the items are the pupils' attitude towards the European Union, their disposition to mobility, and their knowledge of both English and ICT.

2) I have checked everything now! From a linguistic point of view, everything was just perfect. Mainly minor mistakes due to tiredness. (Make sure to check every paragraph).

This sentence seems to be more of a statement rather than a question. However, if you are looking to assess the content of this sentence, you can conclude that the writer has checked everything and found it to be nearly perfect with only minor mistakes due to tiredness. The writer also advises to check every paragraph.

3) By the way, it would be nice if your principal could drop a few lines (in Italian) to our school's principal telling him he was glad to meet us during our preliminary meeting and demonstrating his appreciation for our mutual cooperation and efforts. Both of us have worked really hard on the project and deserve a formal congratulation on behalf of our principals.

The question here is whether it would be nice for the writer's principal to send a message to the school's principal. In this case, the answer depends on your opinion or the opinion of the person you are asking. Generally, expressing appreciation and acknowledging mutual cooperation and efforts is considered polite and encourages strong professional relationships.

4) No one here knows about my efforts as I did almost everything by myself. As you know, I’m not going to receive any money from it! I did it for a right cause and now.

The question here is whether the writer's efforts are known to anyone. Based on the information given, the answer is no, as no one there knows about the writer's efforts. The writer also mentions that they are not expecting any financial compensation and did it for a "right cause" (the cause is not specified).

5) I’m really very pleased that our project will be supported by a German Member of Parliament. Good luck with your daughter. Luckily, my son has fully recovered from the flu! Let me know if there is anything you can’t understand.

This sentence doesn't seem to have a direct question, but if we look closely, there seems to be an expression of satisfaction about the project being supported by a German Member of Parliament. The writer also extends good luck wishes to the recipient regarding their daughter and informs them that their son has fully recovered from the flu. The writer also offers assistance if there is anything the recipient doesn't understand.

I hope this explanation clarifies the content of the sentences you provided. Let me know if you have any more questions!