That is a feature, right click the red line to maximize the tool bar again, right click to minimize the tool bar. Anytime you right click the toolbar . . . it will minimize. It is intended to give you a less cluttered screen. The lines are your heath, mana and stamina levels. At higher resolutions they are difficult to see. . . =)
To drink a potion via the toolbar, left click the browse potion icon and left click the potion you want to drink. A link is much quicker but is only good while you have the particular potion. You can also leave the potion browser open and left click the potions during game play rather than using a linked F key.
If you want to use an active skill (it's icon is in the toolbar), right click the game screen rather than the tool bar icon. Example would be having the lock pick skill active (icon is on the toolbar). Right click the game screen anywhere besides the toolbar than left click the chest to unlock. If you have the lightning skill active (icon is in the toolbar) just right click the enemy to use the skill, no need to right click the game screen first. Some skills require the right clicking of the game screen before using (lock picking, repair) other skills do not, it will become clear which do and do not as you play. Anyway, right click the UI will cause it to minimize.
If you are out of a potion, the F key linked to the potion no longer works. You may need to relink the F key. I will post the basics when I find my image again . . . =)
Edit: here is an image about linking F keys. Mostly about skills but it works the same for potions. Click the Browse Potions icon (top row, far right) and see if the F key is still linked to the potion, the linked F key will be in the bottom left corner of a potion icon, if not relink it by holding the mouse pointer over the potion and pressing the F key you want to link with the potion. The link is good as long as you have the potion it is linked to.
Also, if you are pressing the CTRL key, you cannot drink potions or run away.