but then it has happened that Twitter has locked my Twitter account for no clear reason and now I cannot log into the protal any more. I have reached already the Silver level there, but I haven't input my Xaya wallet yet. So what could I do now?
Your (locked) Twitter account should normally not be the reason, why you can't log into the portal. With portal I guess you mean the widget on xaya.io. By clicking sign in, you will have to put your email address in and will get a sign back in link via email. This should work even with your Twitter account locked. You can then put your CHI address in to the widget.
In fact I have then signed up with my email but is seems to be another account, I didn't find trace of my bounties and the silver level, all the bounties are still to be earned.
One month have passed and still no way to log in with Twitter any more and logging with email leads me to a new and empty account. I have managed to log in with a link received by email but all I find inside is that the Campaign 1 has finished - and I never had a chance to insert my wallet there.