I still have a few sentences to check. I really hope you can help me check them. I added a few more sentences.

1)I think the best thing to do is working at a passion because in this way you'll work better than anyone else.
2)You feel the need to go to work.
3) If you work at the passion, the work itself makes you happy and motivates you to do your best every day.
4) As I haven't heard from you since last week, I've decided to give my students the names of their Irish partners.
5) They will send them their first email using the email address we created for the project. I really hope they will get a reply from your students.
6) One student still hasn't got a partner. She is looking forward to having one, too. I hope you had a nice Easter.
7) She has taken over as the head of the family business.
I'd prefer to work at my passion because I could fulfill myself completely.
8) The teapot came apart in my hands and I burned myself/scalded myself (I got burned).

Are tenses correct?
If I worked, I would work at a job..
When I work, I will certainly work at developing a career.

5) They will send them their first email using the email address we created for the project. I really hope they will get replies from your students.

(Plural students = plural replies)

All other sentences are fine.

And yes, the tenses in the last two sentences are fine, too.

1) The sentence is grammatically correct. However, if you want to make it clearer, you can rephrase it to "I think the best thing to do is to work at something you are passionate about because it allows you to work more effectively and outperform others."

2) The sentence is grammatically correct. It expresses a personal feeling or desire to go to work.

3) The sentence is grammatically correct. It highlights the idea that working on something you are passionate about brings happiness and motivation to give your best effort every day.

4) The sentence is grammatically correct. It explains the action the speaker took due to not hearing from the recipient since the previous week.

5) The sentence is grammatically correct. It describes the plans for the students to send their first email to their Irish partners using the project's designated email address, with the hope of receiving a response.

6) The sentence is grammatically correct. It mentions that one student is still without a partner and expresses hope for them to have one. It also includes a kind greeting for Easter.

7) The sentence is grammatically correct. It states that she has taken on the role of leading the family business.

8) The sentence is grammatically correct. It describes a situation where the teapot fell apart in the speaker's hands, resulting in them getting burned.

Regarding your additional questions:

- The tenses in the first sentence are correct. The use of the past tense "haven't heard" and "decided" suggests that it is referring to a past event.
- The second sentence is a conditional statement. The tenses are correct, with the first part expressing a hypothetical situation using the past tense "If I worked" and the second part stating a future possibility using the future tense "I would work..."
- The third sentence is also grammatically correct. It uses the simple present tense "When I work" to indicate an expected future action of developing a career.