Words in the bible associated with hell in the bible are hades, sheol, gehenna and tartaros. Hades/sheol are generally the grave and present state of the dead -as asleep and awaiting resurrection.
Tartaros is generally the state of restraint of the sinning angels (doing only as God allows) until the judgment.

Gehenna is the lake of fire -in which both body and spirit may be destroyed (but that does not mean they necessarily WILL be destroyed). It is also part of God being like a refiner's fire. It may also be a temporary or indefinite unpleasantness and separation -until one is prepared to do what is right.

While studying the subject, the most hopeful scriptures I have found are the following....

Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is. If any man's work abide which he hath built thereupon, he shall receive a reward. If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.

But now is Christ risen from the dead, and become the firstfruits of them that slept. For since by man came death, by man came also the resurrection of the dead. For as in Adam all die, even so in Christ shall all be made alive. But every man in his own order: Christ the firstfruits; afterward they that are Christ's at his coming. Then cometh the end, when he shall have delivered up the kingdom to God, even the Father; when he shall have put down all rule and all authority and power. For he must reign, till he hath put all enemies under his feet. The last enemy that shall be destroyed is death.

Sex is sex you like it or you do

Sex without marriage is fornication, lust, mental suffering ...

yes it's correct

yes

I believe it is but yet so difficult..

You're right!
All this is very difficult.
All life consists of such difficult questions.
Educational institutions do not teach where to find the right answers to these questions.

And the Bible has answers to these and all other questions.
And it doesn't matter that it was written a long time ago. The main thing is that it has answers to all people's questions!

Casual sex can be no good if over indulged. With a partner you respect it is very fine. The fact a guy in robes mumbled some words over you does not change bad into good, it is simply symbolic of your commitment.

Disease transmission and unwanted pregnancy are major downsides of casual sex but can be managed. Gays don't have to worry about pregnancy

Hard one

considering the frequency after marriage, it must be a sin to have sex being married...

sexul

i'm not going to look it up but it is a sin in both new and old testament...sadly the world today has gone so far with that we have open marriages , open relationships, and so on so having one partner doesn't seem so bad in comparison.
i personally believe you will save yourself a lot of heartache by not having pre marital sex...and that is why commandments and statutes are made to help us not to hinder us but we have gone astray so long it is hard for most people to know which way is up.
to the op it is good that you ask the question....

yaaa good for enjoy

There's no such thing as sin, only laws.

i would not know about that ... i aint married now !!!

Sin is not forever unless you make it forever. All you have to do is ask for forgiveness and it will happen. Sex should not only be physical, there needs to be an emotional attachment as well.
Just my opinion, it doesn’t mean I am correct, just how I feel.

If I am not mistaken:

-It is sinful altogether in Christianity.
-It is not sinful at all in Islam.
-It is sinful altogether in Buddhism.
-It is sinful in Judaism.

Best to ask a local expert in your own religion.

It's a major sin in Islam, you're gonna get stoned to death if you are married and had sex with another partner outside marriage, or get whipped (100 lashes) if you're not married.

Yeah but that is another story, it differs from what you asked initially. Also can't man have multiple wives in Islam? If it is so then just get married to all, case solved