It seems unreasonable to me to expect to be B1 in 6 months with 2 hours of class per week.

I've been learning German 2 hours a week + homework for 2 years and I'm not yet B1 in German. We are 4 students with one teacher and, from what I understand, we are not particularly slow.

Maybe German is really harder to learn than other languages, but probably not 2x or 4x as French (I'm French).

I'm probably C2 comprehension, C1 speaking in German. I self-taught to high B2 (based off placement into that level in a Goethe Institut Intesivkurs) in 15 months of 2 hours a day. I studied 1-2 hours per day on average and did not miss a single day.

2 hours a week to B1 in German as an English speak seems totally impossible. I was probably B1 in 6 months at the level of study I described. I studied 5 years of Latin prior to starting so the case system wasn't an additional learning curve. Your pace honestly seems standard.

People talk of "difficult" languages in absolute terms, but there is always the question of where one is coming from.

English shares a significant amounts of structure and words with French, so French ends up being relatively straightforward to learn for a motivated English speaker - the only real difference is the amount of tenses, which OP unsurprisingly still struggles with. I bet you, as a French speaker, would grasp Italian very quickly - much faster than most Chinese likely ever will.

German ended up sharing much less with Romance languages, so it stands to reason that it would take 2x-3x the effort of going from English to French.

I think language classes are in itself slow. Duolingo is a lot faster. After Duolingo you should read texts in the language (B1-B2 maybe) and then you will start being able to listen to arbitrary native speakers (which I don't think is practicable before C1).

French has plenty of difficulty in orthography and some in grammar. Maybe the grammar is slightly less complex than German, but only slightly. But I'd say for someone from another language that is easily overshadowed by prior experience in English or Spanish or similar.

In my experience duolingo on its own doesn't get you anywhere past A1 or maaaaybe A2 in German.

The current course (from English) should get you well past that.

Try to immerse yourself as much as you can! I think one key factor is to get your brain to think in/about the new language, all the time.

why would you say so?

There are many linguists who think it's more important to get comprehensible input, then produce comprehensible output [0]

[0] https://www.youtube.com/watch?v=CwjkqUBztiM

Paying someone to speak to you is going to provide comprehensible input and output.

Isn't individually targeted comprehensible input a large part of a 1-on-1 class? I would expect a good teacher to speak a lot during those 2 hours, and to properly adjust his speech so that's always pushing the boundaries of what the student can understand.

That approach feels intuitively wrong to me[1]; people who watch sports don't automatically become good athletes. People who look at pictures don't automatically become good at drawing. People who read don't automatically become good authors. People who watch cooking shows on TV don't automatically become good at cooking. Students who watch programming videos notoriously don't automatically become able to code anything the compiler accepts. Reviewing study notes by re-reading them is one of the less effective study strategies, compared to flashcards which prompt you to recall and generate answers from your memories.

Surely yes you need to adjust to the sound of a foreign language, but with no feedback loop of trying to speak and having another person feedback, how do you adjust?

Listening to hours of completely foreign language won't make you understand what the words are or what they mean, so "comprehensible" input includes weasel words that require you to already know the language before you can learn it. It's all over a bit weird.

Don't people say some of the most effective ways to learn are the immersion courses where you go to a retreat and speak only that language for weeks at a time, studying and learning 8 hrs+/day and then there are people who spend years reading or listening but aren't confident to speak anything. But are there people who spend years speaking with fluent speakers who still report they don't know the language?

[1] inb4 "hurr think you know better than professional linguists"

Check out the studies and lectures by Stephen Krashen if you want to hear from an academic that's been studying this for 40 years.

I'm on week 8 of a weekly 90 minute Italian course. My wife and I both are in it, 8 other students and the class is held over Zoom. I've actually been pleasantly surprised with my progress. We study a bit outside of class and there is some casual homework but I'm excited to see after taking a few more levels with the teacher.

I do wish the class was twice a week for more forced cadence of practice but that's an adult problem.