If you know, could you please tell me how to type that "u" or kind language should I set for my keyboard?
There is an Esperanto keyboard, but you have to download it and install it separately. The easy workaround is that for any of the special characters, if you just type 'x' after it, the system will accept it as correct. So for aǔ you can type aux, or for ŝanĝis you can type sxangxis.
It depends on what system you have; if you google it, it should be pretty easy to find.
Depends on if you ar using a smaphone download and inatall "AnySoftKeyboard" from Play Store or F-Droid. If you are on dewktop/laptop then uh can.choose Esperanto keyboard in language/keyboard settings.
Also, on my computer it just shows all special characters below the responses box.