(someone) promised (someone) that (clause)

This is how to describe a promise. The word "promise" requires two pieces of information: who the promise was made to, and what the promise was. The "who" part comes right after the word "promise":

She promised him that she'd pay him back.

Sometimes you can leave out information about who the promise was made to:

She promised that she'd pay him back.

You can also say it this way:

She promised to pay him back.

To tell what the promise is, use a clause like this:

I promise that I'll take good care of him!

Notice that if the "promise" is happening now, you use "will". If the promise happened in the past, you use "would":

She promised that she would take good care of him.

be responsible for (something)

"Being responsible for" something means that you have to make sure that something is taken care of. For example:

I was responsible for taking care of my little brother.

This means that it was your job to take care of your brother. If something bad happened to your brother, you would be blamed for it.

Here's an example that you might see on a sign in the locker room at a gym:

Total Fitness club is not responsible for any missing or stolen items.

This means that the gym will not have to pay for your things if they get stolen.