Here are the corrections for the mistakes in each sentence:

1. **She likes shopping** window with her friends on Sunday **evenings**.
- **Correction:** Change "shopping window" to "shopping" (the phrase should be "shopping with her friends").

2. **Tet is** meaningful to everyone although it is a **time for family reunion**.
- **Correction:** Change "a time for family reunion" to "time for family reunions" (for grammatical consistency).

3. **When I last** saw them, they tried to find a new flat in the city **centre**.
- **Correction:** No correction needed if "centre" is British English, but in American English, change it to "center."

4. **Using computers much** can have negative effects on both their minds **or** the body.
- **Correction:** Change "much" to "too much" and "or" to "and" (it should read "Using computers too much can have negative effects on both their minds and the body.")

5. **Would you like** going to Ha Long Bay with me next summer?
- **Correction:** Change "going" to "to go" (it should be "Would you like to go...").

So, the corrected sentences would be:

1. She likes shopping with her friends on Sunday evenings.
2. Tet is meaningful to everyone although it is time for family reunions.
3. When I last saw them, they tried to find a new flat in the city center. (or "centre" depending on the preferred version).
4. Using computers too much can have negative effects on both their minds and the body.
5. Would you like to go to Ha Long Bay with me next summer?