A little investigation leads to the method:
1. Basically, we may learn current language by using request.lang
2. We may show / not show the element bu using t-if
Such approach allow making different structure for various languages. For example, to show different types of question marks for en_US and de_DE languages:
<div class="mt16 col-md-5" t-if="request.lang == 'en_US'">
<span style="color:#FF0000;">
<span class="mb16 fa fa-question-circle fa-5x" src="" style="animation-play-state: paused; transition: none"/>
</span>
</div>
<div class="mt16 col-md-5" t-if="request.lang == 'de_DE'">
<span style="color:#FF0000;">
<span class="mb16 fa fa-question fa-5x" src="" style="animation-play-state: paused; transition: none"/>
</span>
</div>
It is important, that no controller rewriting is required, only xml change.
A problem is that element in not default language may be changed only via HTML editor, since Website editor is for default language.