How to disable this?

[BS]

I've been searching in the UI settings and the Quest Log and I seem to find no way to

disable the big yellow letters with quest related instructions that display in the mid of the UI.

Is there any way to disable those?

[Els]

Can you provide a screenshot ? 
You meant when you have a message at the middle of your screen with an exclamation mark icon preceding it ?

[BS]

Yes. Exactly this.

Quest related instructions, like go speak to a NPC,or carry a bundle there etc etc.