Understood. Even before reading this it occurred to me that I should first use the discussion area for suggestions and subsequently just finished doing so for a later unit. Your point on preserving the contemporary styles is well taken. Perhaps I'm just not taking this that seriously. It's certainly not a question of competition for me. I did not know about Duolingo Immersion. We need more participants in this project. (By the way, I did talk to a few members of "den norske fiskeklubben av San Diego" about helping. I'll try that again this coming Friday.) I'm a Dashiell Hammett fan and his writing style, which was from the same era, the 1920s and 30s, definitely avoided outmoded English expressions of any kind unless he wanted to ridicule an affectatious way of speaking. Actually, in this example I would have expected "fordi" instead of "for". Then there's the element of character development through their conversation styles. Maybe Elvestad is painting a picture of a young bar maid with higher aspirations, a romantic. I dunno. Thank you very much for the info. It gives me something to think about while I'm running which I'm going out to do now. I'll try to get to translating every day but that's a challenge.

Definitely not modern. But there is some value in preserving the historic style and atmosphere. I don't think that one 'for' will do that, but it's a choice. ChatGPT often provides alternative translations based on the reader's perspective.
Another point which I think I've made before. In Translatihan, we generally leave it to the original translator to edit the translation. Other translators provide their suggestions/comments in the Discussion section, which the original translator may or may not wish to incorporate, usually, after some discussion. You may wish to look at other language couples for how these discussions occur. e.g., see English->French or Spanish->English. Our approach differs from that used by Duolingo Immersion, the website that preceded Translatihan and was terminated by Duolingo in 2017. It was common to see pairs of translators collaborating. Instead of supplying an entirely new translation, one of them would slightly modify an existing translation, which was then quickly upvoted by his/her buddy. In this way, pairs of translators moved swiftly through the ranks to reach the top of the language combo. Every 100 upvotes moved you into a higher bracket. Translation became more of a competitive sport than an enjoyable pastime. If you were using Duolingo Immersion at the time, you'd know what I'm talking about. When we set up Translatihan, we (my son Ryan and I) decided to tone down the competitive spirit that was prevalent in Duolingo. We emphasized the original translator's contribution by leaving it up to them (singular) to make the edits in the translation. Since translators take turns translating, everyone ends up earning credits through upvotes. The Spanish->English team is a good example. There are five translators, each translating about 5 units at a time, and they translate every day. Comments are made, and the final translation is reached by consensus. The collective effort ensures that an optimal translation emerges, approaching the quality of a good literary translation.
Hope this comment helps.

Well Okay. But I can easily imagine a comedian poking fun at "FOR I have..." using sarcastic exaggerated dramatic hand gestures. I do see the match-up with Norwegian phrasing, but modern? Didn't ChatGPT say that it preserves a slightly older tone? And conversational? Definitely not, at least not in American English, not without inviting sarcastic lampooning. It sounds affectatious.

I asked ChatGPT: Would you prefer 'for' over 'because'? The response: In this literary context, I would prefer “for” over “because.”

for preserves a slightly older, reflective narrative tone that matches the Norwegian phrasing well.
because it sounds more modern, direct, and conversational.
Take your pick.

The use of "for" in place of "because" seems at least more rare in conversational English, and certainly more literary.