A question

[SaigoNoBan]

The adverb for "Dangerous" is "Dangerously" and:

* い-Adjectives build it by replacing the last い with く：
危なく住んでいます　（あぶなく　すんでいます） = (I) live dangerously

* な-Adjectives are followed by に：
丁寧に答えました　（ていねいに　こたえました）　=　(He) replied politely

When you say that (something) is dangerous, "dangerous" is still an adjective, so it is perfectly correct to say,　（Subject）　危ない（あぶない）です

On a side note, I hope you don't mind if I say that I think it would be easier for you （and for the rest of us）　if　you　learned at least a minimum level of English before posting questions about　Japanese　on an English-speaking forum...

[SaigoNoBan]

I don't know if there is an idiomatic expression for "fall in love", but AFAIK I'd say:

It is dangerous to fall in love: 好きになることは危ない　（すき　に　なる　こと　は　あぶない）

愛のことは危ないでしょう　（あい　の　こと　は　あぶない　でしょう）　＝　The business (the thing) about love is probably dangerous

友達いることも危ない　（ともだち　いる　こと　も　あぶない）　＝　The fact of being friends is dangerous too

[Harisenbon]

Fall in love
恋に落ちる
こいにおちる