Deutsche Grammatik irrational?

A language is created over a long period (century) of use, through many different people. It is clear that not everything fits together seamlessly, but the language is a great entity that is “historically grown” (and not planned).

So some things are certainly illogical or irrational. Some people don’t fit together. Nevertheless, German is certainly not completely arbitrary, there are several patterns that are consistent (for example, the participatory is always formed with ge-, so have been, said, done, sung etc.).

What is difficult to predict is the formation of a bluete in the strong verbs.
singing – sang – Other, but sitting – sat – you have (not “sutting” – in Swedish, by the way, the participle is suttit, with -u- and with -t-).
In addition, there are weak verbs sweating – sweating – sweating, although they are regularly formed (and without ablue), but one wonders where one should know whether the verb is now strong or weak.

Does it mean “wrinkle” or “wunk”? When I get woken, I always have to think: if you say “wank”? wave – wank – woken or wave – waved – woken.

In this respect it is a mixture of regularity and (historically grown) wild growth, which seems to me most appropriate.

North-German languages also know Ablautserie, even there they are quite complex and not always consistent predictable. In Iceland there are, for example,
ég dett (I fall) ég datt (I fell) ég hefur dottið (I fell) e-a-o as much as I met, I met.

Also Icelandic has weak verbs (setja = set, so setja – setti – sett).

Icelandic also shows many ablautes in the Nomen. Vocals often change in pairs. That means General (a) field, in plural vellir, and in Genitiv Plural the.
The battery of Anna is o. There are rules, but it’s not always up.

Almost all languages have irregularities somewhere, some more, some less.