the heart system
I find that system for losing a heart every time you make a mistake totally ridiculous because after 3 mistakes you are sent back. Most of my mistakes come from the audio because there is a serious problem with its quality. The level right now for me is actually too easy and gets boring, but if 3 mistakes (hearts) throw me out it's no fun. Can I get rid of that stupid heart system and work at my own pace????
If the audio is giving you problems, try slowing it down. Sometimes I also have issues hearing the audio at full speed, but slowing it down solves this problem completely. The heart system is the only check and balance system that DL uses to make sure you have reached a basic proficiency in each skill.
I don't see how I can make it slower and often the letters seem to sound quite different from what you claim they are. I don't see why the system should care if I made 3 mistakes and then doesn't let me advance to a level that would be less boring because I wouldn't have to deal with constant repetitions of too easy sentences. I can judge my own proficiency much better than your system.
When you are doing a listen and type in Spanish exercise, you will notice a large speaker icon (that you can click to repeat the audio), and directly underneath it is an icon that looks like turtle. Click this and the audio will play slower (putting emphasis to separate each word).
Another way to play to audio slower during these exercises it to click ctrl+shift+space