What does "I am feeling hot " mean in causal and slang sense? For example can we say it has a meaning like
The temperature is high so you feel the heat and sweating maybe.
You were stimulated sexually and have an intercourse maybe.
You think you attract some people sexually,can be used with preposition for .
and another question what is the best way to say for the first meaning?
You are right that “feeling hot” can mean feeling a high body temperature, due to heat in the air or due to a fever, or sexual arousal, because of the body heat resulting from blood flow. The sexual meaning of “hot” can be extended even further, to people who look sexually attractive (“She looks hot!”), and even to the feeling that one has a sexually attractive appearance (“I feel hot”), though this is unusual. However, “I'm hot for someone” doesn’t mean that you think they find you attractive, it means that you find them attractive (hence, your own feeling because of and drawing you to that person). Also, that sense is normally used with a linking verb, not with “feel”.
If you want to avoid the sexual meaning, you are in luck: “I feel hot” in the sense of feeling that one's appearance is sexually attractive, is so rare that in most contexts, people won’t hear it that way. Usually someone would hear “I feel hot” in the plain, ordinary sense of feeling that one's body temperature is too high. In context, it’s usually perfectly clear. For example:
I think I have a fever. I’m feeling hot.
(Outdoors when it's 95ºF/35ºC.) I'm feeling hot.
The sentence “You look hot” is more prone to being heard in its sexual meaning even in inappropriate contexts.
One way you can avoid the sexual meaning is to say “warm” instead of “hot”. In a situation where you’re likely to talk about warmth, such as on a cold, winter's day, this won’t work. But in almost any other situation, like a hot day or someone struggling with a fever, if you say “you look warm”, people will hear that as “warm enough to be remarkable, in a situation where being warm is unremarkable, therefore you must mean uncomfortably hot”.
