Manuals Library (manualslib) is the best site for manuals by a country mile. I just opened this one in less than a second. the website www.manuals.is has it, but it is not a good viewing format.
You can find Adler Manuals on following links. I am sorry I could not find 310 Model. But most of the time, companies make one manual for many models. I hope you can find a manual matching to your machine.
D?rkopp Adler sewing machine manualsUseful Manuals (bootmaker.com)
u need a silicon based nylon thread and a larger needle. needle may be getting hot too depending on thickness of work. spray some silicon on upper thread.