Battery, starter, LiMa, I don’t know.

Moin Hab since last night once again small techn. Problems And I wanted to do something again fast last night. So, in the car open, jumped in, keys in, turned around and…? And? Klack. Again turned…. Klack. And again…. Klack. Hmm, Schei..e thought and first looked at the voltmeter. At least showed still around the 10V. So Karre pushed on and drove off. Let the battery charge nice (about 1 hour in the stand). And? No, this time no crack, but only on the last pusher. So I first clamped the bill and the warranty certificate of the battery under the arm and drove to the FOH. Jo, then the first came out with the battery tester and first read out errors. Result of the test: “battery good”. Hmm, ok, then he fetched the current tester and measured if there are power thieves somewhere. Gen.: 0.17 A resting current. So fine. Car in the workshop danger. The result: Although alternator supplies battery with voltage, but only with approx. 30-35 A. This is a normal value, but it does not charge any more when the threshing number is raised substantially. Then he told me that it may also be the starter. Bad ground connection or similar. Well, what do I do now? Tomorrow morning it will probably go clack again and nothing. Does anyone have any guess what it might be? Or someone else will check the alternator. have had the same problem? I am grateful for every tip. Greetings Kevin