Most likely you been phished.

Since you still have access to your account follow these steps do not skip any, as this is to help you secure your account.
1. Scan for malware https://www.malwarebytes.com/
2. Deauthorize all other devices https://psteamproxy.yuanyoumao.com/twofactor/manage
3. Change passwords from a clean computer
4. Generate new backup codes for your Mobile App https://psteamproxy.yuanyoumao.com/twofactor/manage
5. Revoke the API key https://psteamcommunity.yuanyoumao.com/dev/apikey (there should be nothing in the APIKEY)

Most common reason people get accounts hijack for any service really are as followed.
- Sharing account infomation with others. <--- Very common with impersonators, pretending to be Steam admin / support.
- Logging in on phishing sites. <--- Very common with skin gambling sites.
- Downloading / Installing Virus / Keylogger on your system.
- Using public devices that has keyloggers, such as cyber cafe, school computers, and etc...
- Storing your login credentials on a unsecured service that others has access to view.
- Using same login credentials for all your things, or using same login credentials on another service that had a data leak. Yes it does matter because even if it not related to Steam, if using same login credentials, hijackers will try to use those credentials to see what services you use with those credentials. https://haveibeenpwned.com/
https://m.youtube.com/watch?v=9TRR6lHviQc

Steam support will not return your traded items.
https://support.steampowered.com/kb_article.php?ref=9958-MJDG-3003

So i will never see my skins again ?

引用自 Paranoia♛：

So i will never see my skins again ?

引用自 Dr.Shadowds 🐉：

Steam support will not return your traded items.
https://support.steampowered.com/kb_article.php?ref=9958-MJDG-3003

What i can do to get my skins back ?

引用自 Paranoia♛：

What i can do to get my skins back ?

Buy them again, because Valve's not going to reimburse you for them.

引用自 Paranoia♛：

What i can do to get my skins back ?

Only one thing: learn to read.

引用自 Dr.Shadowds 🐉：

Steam support will not return your traded items.
https://support.steampowered.com/kb_article.php?ref=9958-MJDG-3003

As you can see and as we tell you the THIRD time now, gone items are gone and won't get recovered.

It's entirely your fault that someone had access to your account and you're responsible for all actions taken in meanwhile, such as gifting away your inventory.

NotEvenBlurm Bro are you okay? nobody have acces to my account, wtf are you talking about...
it was a keyloger maybe.

引用自 Paranoia♛：

nobody have acces to my account, wtf are you talking about...

You sure? Because this...

引用自 Paranoia♛：

Someone got my account and trade all my skins

...is LITERALLY the definition of having access to your account. Or how to you think did your inventory change it's owner, magic? Becoming digital feet to flee?

引用自 Paranoia♛：

it was a keyloger maybe.

And this "maybe" shows up that you don't care about other user's replies... If you would have done the steps thenDoc wrote down in answer #1 you'd know the reason.

I do not understand why you are so toxic, you can explain nicely, and I tell you once again no one has access to my account, anyway thanks for the advice, next time someone asks you for help

引用自 Paranoia♛：

I do not understand why you are so toxic, you can explain nicely, and I tell you once again no one has access to my account, anyway thanks for the advice, next time someone asks you for help

Just to be safe I would recommend following the steps from step 1

The malwarebytes Site ?

Just follow the steps in the first post.

引用自 Paranoia♛：

The malwarebytes Site ?

All the steps
Its to be safe

i made all the steps, it`s clean

idk how he scam me, it`s ♥♥♥♥♥♥♥ imposible