No it doesn't only mean wanting to hook up, depending on your definition of hooking up. It does mean romantic interest or physical attraction though.

Also to answer why is usually almost impossible in languages. Often meanings of words and phrases just evolved that way without being able to know why.

'I have a thing for you' isn't really used for romantic gestures, instead it's stating the person's sexual attraction to the person they're speaking to. The same can be said for:

'I have a thing for women that ____'

'I have a thing for men that _____'

'I have a thing for leather' (in this case 'I have a thing for someone dressed in leather')

'I have a thing for red heads'

Etc...

I hope this helps :)

It's simple anyway he gets something good whether it's a gift or a romantic thing

It means someone wants to hook up only??

The dictionary definition of "crash" for the Spanish? Brazilian/ Portuguese? teacher whatever he may be. Is "to come to a sudden stop with catastrophic consequences" which is why planes, boats, cars. motorbikes and computers "crash". and why we say can I crash at your place only if we know we are going to hit the bed and fall to sleep instantly because we are so tired we will be out of it until the next morning.

Talking of coming to a sudden stop with catastrophic consequences, the comment has done exactly that "crashed the question".

And why we say "gate crashed" a party or anything else.

And also why we say for an emergency team at a hospital "a crash team" that is called when a patient has a heart attack or similar. The patient will have crashed come to a sudden stop with catastrophic consequences.