Overtaking (above) and stopping on the carriageway (below). Notice that when overtaking it is seldom necessary to signal left when moving back in front of the overtaken vehicle. When overtaking, you should be travelling in a straight line. When stopping on the carriageway, a signal is enough where it is obvious that there is no left turn ahead. This will avoid confusing others, but the correct hand signal doesn't do any harm.
When you are driving you use signals in order to inform, not to instruct. Giving the correct sign...