Sure! Here are the sentences changed to convey the same meaning:

4. She could share her feelings on social media; she could inform her teacher about it.
5. I enjoy school; I like learning new things and spending time with my classmates.
6. You must arrive at the concert early; otherwise, you risk not having a seat.
7. She is careful; however, she still forgets her phone when going out.
8. William decided to study late at night; as a result, he drank a cup of coffee.
9. Henry was very tired yesterday morning; thus, he couldn't attend school.
10. Ms. Susan's lecture was lengthy; it was also quite boring.

For the fill-in-the-blank section:
1. It was raining, so we stayed at home and watched a film.
2. I want to buy a new pair of shoes, but I don’t have enough money.
3. She had a terrible headache last night; therefore, she drank a lot of wine.
4. I like eating pancakes; however, I never eat cream cakes because I don’t like them.
5. Would you like chocolate or biscuits with your coffee?
6. My math homework is very challenging, so we can walk to the stadium.
7. She finds the exams very hard; nonetheless, she always gets good marks.
8. You’ll be late for work if you drink too much water to lose weight.
9. I have a lot of exercises to do this evening; consequently, you will feel lethargic.
10. I can’t find time to chat with you; my friend has a problem with his lungs.
11. I like to watch documentaries on TV, but I have to pay attention to my studies.
12. Fill in the sentence with a suitable coordinating conjunction: I will need your help to do my homework.
13. I will still want to buy it; however, she missed the bus.
14. If the weather is fine, let’s go outside; otherwise, we can stay home.
15. While I was reading a magazine, I noticed it was very cold.
16. I am very tired now; in fact, I don’t want to go shopping with you.

Feel free to ask if you need more help!