Loss of power only limits your ability to climb higher or maintain altitude. Most of the new paramotors have an electric starter. One can restart the engine and continue. Supposing you are unable to start the engine for some reason, then you will glide down gently like a normal non-powered paraglider. Usually when you get into a thermal and going up steadily, it is prudent to switch off the engine and conserve fuel. Once you are comfortable in paramotoring the engine is switched off on a committed final approach, just before landing.