What does a dotted minim/half note =c.60 mean? What does the c mean? And how much BPM is this?
It means that you play the piece at 60 BPM per dotted minum, which is the same as 180 BPM per crotchet. The C, as far as I know is an abbreviation for circa which means around. So around 60 BPM.
The writer has designated the dotted minim as the 'beat', and said that there will be about 60 of them in a minute. This makes each bar last just one second. It's not easy to time bars in that way, but setting a metronome at 60bpm will help you play each first note of each bar on a click.
If you wanted a click on each crotchet, then set the metronome for a pretty quick 180bpm, and play the left hand part along to that. A student of mine would say 'el-e-phant' for each bar. and keep time to that.