From: US Midwest
The Strategy Guide just below the Game Manual buttons on the main screen when you open WiE has lots of helpful tips. You can also try reading through some of the after-action reports.
It is hard to know what to suggest without seeing what he is doing. You say it is summer 43, which victory cities(Leningrad, Moscow, Stalingrad) has he taken by now, if any? If none, I would guess that he is not focusing his forces enough. You need to keep up the pressure all along the front, but the best Axis players will focus most of their aircraft and tanks on one objective at a time, ensuring its fall. If you divide your forces evenly and attack all 3 cities at once, your forces may be too divided to take any of them. You get bogged down, the WAllies invade, and its all over.
The other thing that will stall the Axis in the East is poor supply management. Keep your HQ's in cities so they generate maximum supply. German tanks are very powerful, but at 50% readiness, they are only half as good. Learn the HQ chaining rules, how one HQ can supply another. You will be surprised how much more effective your units are when in good supply.
Just some basic suggestions. The best way to learn how to play Axis is to play a good Axis player. This will also give you a chance to see things from the other side, the vulnerabilities of the Soviets become much clearer when you are playing them.
Your friend may need to manage his techs a little better as well. You mention that in summer 43 he is at advanced tanks 3, he should probably be at AT 4 by that time. That is a critical tech for the Germans, they cannot afford to neglect it. The superiority of their tanks is one of the Germans main advantages, if they lose it, the offensives will stall.
Lock up your wife and children now,
It's time to wield the blade..