How to make my activities from public to private?

You can easily change back your publicly shared activity into private, anytime.

1. Log in to your account. Go to My Activities.
2. Beside the activity title, click on the three dots icon and press the Share button.
3. Click on the Share page. 
4. Click the Private button.

Another option is to go to the activity page.

1. Select the Share button.

2. Click the Share page

3. Then click on Private

See: How to make my activities public?