MOST of those connections are just simple multiple-wires-coming-together... if you are concerned, use an ohm-meter and there should be continuity between every pin in the same color code.
The wiring diagram for that model will show the other connections that are made, using the board: the top two center ones are connected by the little ceramic fuse so dear to the germanic engineers, where you have the metal/glass ones: #15 is live, going through the fuse to feed #15U; #58 is live, going through the fuse to feed #58U. (by "live", I mean that they are fed from the ignition switch and are "live" when the switch is "on".. the only real "live all the time" wires in the bucket are the red ones coming to the ignition switch)
You can test the diode with your ohm-meter as well: it connects "LKK" to the brown/yellow right next to it (I can't read your board, am too lazy to go find my Haynes.....
)... Reminder: a diode is an electrical check-valve, or one-way valve: electricity can only flow one way. So, put the leads on either side of the diode, and it should read continuous one way, and not continuous with the leads reversed (red is +, black is -).....
What looks like a hodge-podge is actually VERY simple and quite orderly.
I am vaguely remembering that I could not find the terminal "LKK" in the Haynes manual, but the color coding works, so no matter.
I actually LIKE electrical work and electrical sleuthing (twisted, huh....!), so let me know if I can help in any way.