Hi everybody,
Thank you very much LeGaulois who gave me the good Telegram tipp!
I chatted with the responsible woman of Huobi through Telegram in the Telegram channel of Huobi. It was not that easy to catch her attention. I chatted long with her. She proposed me again and gain to change my browser and to use different websites of Huobi (huobi.com, huobi.pro, huobi blablabla). And she asked me again and again the same questions. At the end she advised me to write to
support@huobi.pro.
I sent to the support an email where I explained clearly my problem with a photo and a screenfilm of the impossible login.
The next day, the responsible woman oh Huobi wrote me through Telegram that it should now be OK. Indeed, I could endly login :-) (-: