Persona:input field disappears on mobile devices

[mechanix]

When creating a new topic on a mobile browser, the input field disappears so you can't see what you type. This is because, other than replying to a topic, the category list is shown.
Is there a quick fix for this as the most users of my forum are using mobile devices to creat/reply to topics.
Thank you

[mechanix]

And here is another minor issue:

[mechanix]

Any hint to get this fixed?