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.