Scalding water one minute?

I have recently moved into an apartment with a Pulsacoil A class. I am a single female and really do not have clue about these types of things!
My issue is my hot water is too hot. It's actually scalding and I cant eas this as i do not have mixer tap. The second thing is when i take a shower, if I am in there for more than 15 minutes the water will run cold. I live alone also so it's not that someone has beaten me to it.
Is there something I can do for these problems, adjust the settings or could there be a fault? I was unfortunately not given any documents from my landlord so I have had to google the problem which has brought me to you lovely people.

I am hoping someone can assist me and any help however minor you may think will be greataly appreciated.