"Zoete kers" is a Dutch equivalent of "sweet cherry tree" (Prunus avium).
"Vogel-Kirsche" is a German equivalent of "sweet cherry tree" (Prunus avium).
early spring
"Wild cherry tree," Sweet wild cherry tree" or "Sweet cherry tree" may be English equivalents of "Zoete kers" (Prunus avium).
"Wild cherry tree," "Sweet wild cherry tree" or "Sweet cherry tree" may be English equivalents of Vogel-Kirsche" (Prunus avium).
"Zoete kers" is a Dutch equivalent of "sweet wild cherry tree" (Prunus avium).
"Vogel-Kirsche" is a German equivalent of "sweet wild cherry tree" (Prunus avium).
mid spring or after you pick the cherries
This tree can be pruned from mid-summer to fall, but before the first hard-freeze for your area.
No because one must have sour with sweet
Yes, however, you probably meant cultivar instead of species in this case. In the case of a cultivar, the answer is a qualified no. Most sweet cherries do not pollinate their own varieties. Most sour cherries do. Recent developements have come up with some self-fertile sweet cherry cultivars. Reputible nurseries will tell you which ones you need for which and usually have charts on hand to help.
Prune it after leaf fall. It depends why you want to prune it. Trees dont usually need pruned as it spoils their natural shape. If it has become too large for its space then cut it back but remember pruning causes more growth.