The fields across the top of the "Leistungsbuch" (Book of Achievements or Performance Record Book would be a good translation) are from left to right:
Operational day serial number (you can see these are 1 through x - described as "Feindflug", flight in the face of the enemy, but the first record is actually two flights on the same day)
Evaluation as combat mission (not sure what this means but it seems to be a score - possibly out of 20, which is common in Germany for things like exams. note that it says "Frontflug" - flight over the front line - rather than "Feindflug" so I think this means it involved contact with the enemy)
Aircraft type (not surprisingly, Junkers 88 or 188)
Date
Time out/time back in
Flying time over enemy territory or potentially threatened territory, in minutes
Route
Depth of penetration into enemy territory, km
Contact with enemy fighters or flak
Results of the mission. For example: kill, observation of artillery fire, reconnaissance objective, bomb release (state the drop altitude, type of attack, number of passes over the target, whether or not photographic BDA available, etc)
Authentication: witness or authorising agency (these are all blank, because the previous 5 operational days with 10 flights were authenticated in bulk by the guy who signed across his stamp halfway down the page - a Senior Lieutenant and Command Staff Officer whose signature I can't read, whose stamp says "The accuracy of serials 1 to 5, 5 operational days and 10 combat missions, is hereby confirmed")
As an example, Serial 7 on the 10th of July, 1944 was assessed as a combat mission of grade 13. Yer man launched at 2258 in the Ju188 from Tiraspol for a mission via Kovel, Rovno, and Kasakin, returning to Tiraspol. Tiraspol/Terespol is in present day Moldova, dunno about Kasakin, but the other two way points are in western and central Ukraine. This took him over enemy territory for 3 hours 20 minutes to a depth of 330km. He was engaged by flak of all known calibres and illuminated by searchlights on 34 occasions (!). The aim of the mission was to get battle damage assessment photos (Zielwirkungsbild = "target effects image") of the Kasakin area. I *think* he reports engaging 30 motor vehicles (Kfz. = short for Kraftfahrzeug, motor vehicle) with the aircraft guns (Bordwaffen) but it could be the other way around. He arrived back in Tiraspol at 0300.
The next mission, 10, took a different, shallower route and seems to have been a tactical photo-reconnaissance task: he reports getting photography (LB = either Luftbild, aerial imagery, or Lichtbild, photography) of a 300 vehicle concentration in what I think is a grid square reference, 5135. Analyst comment: that sounds like one of the Soviet armoured divisions of the day, probably best start packing for the next move as they're maximum 130km away.