Howdy,
Yes certainly a Mayfly
The small hind wing should enable you to make some headway toward family, but I haven't looked at these yet so I'd better not try to 'help'
About a year or more ago I tossed some links onto a
scratchpad page - especially check out the links for the website by Jürgen Gaul !! He's quite good with Ephemeroptera and as an added bonus he's 'accessible' through the fora of
entomologie.de and
insektenfotos.de.
Hope it helps
Arp