Can not add new replies into a Forum

Can not add new replies into a Forum

When trying to add a new reply into an existing forum, the cursor does not appear, and it is not possible to write any comment at all. Sometimes, logging out and in, resolve the problem as a workaround, but sometimes don´t.
 
In addition, when selecting an option or tab, we need to click twice in order to receive a response from the system.
 
Can you help us?