I'm self-control" OR "I'm self-controlled"?

[twilit1988]

My dear and respected teachers,
1: "I'm self-control" OR "I'm self-controlled"?
2: "What should I use after ''expert'' (in,at,on)?"
3: "Let's go to the hotel at your expense." correct?

[Seru]

I'll give my best shot.

1) I have "self-control".

2) I am an expert in [field of expertise].

I hope my answers satisfy your thirst for knowledge.

[Snowcake]

My dear and respected teachers,
1: "I'm self-control" OR "I'm self-controlled"?

I am self-controlled.
I have self-control.

2: "What should I use after ''expert'' (in,at,on)?"

An expert in [ field ]
An expert on [ topic, subject ]
An expert at [activity, skill]

I'd say, e.g.,
an expert in physics, in biology, in various fields etc.
an expert on extinct mammals, on Elizabethan drama
an expert at (playing) golf, an expert at inviting the wrong people (ironic), an expert at that kind of difficult diplomacy.


3: "Let's go to the hotel at your expense." correct?

Grammatically fine, but I can't think of a situation where it would be said. It sounds a bit odd to me (and impolite as well). "the hotel also implies that your are talking about a specific hotel.

Let's go to the hotel (room), so you can freshen up.
An airport shuttle bus can be arranged with the hotel at your expense.


Let's wait for another person to answer 3.