It was pretty similiar for me as well. In NRW, Germany.
I was at <4 µg/l (not measureable). Welp.
Took 20k/Week for 8 weeks as well. Felt a lot better, don't know my after result though.
The problem for me was. A few months later I was down to ~7ish again. Looks like I need a daily supplement then.
To be honest, I felt normal before and normal after. I'm not sure what my levels are now (and I feel normal too), but I've started taking weekly Vitamin D pills from DM. They have 5600IU and I've been taking two per week. Will probably just do a blood test in a month or two to see where I stand.
The problem for me was. A few months later I was down to ~7ish again. Looks like I need a daily supplement then.
How did you feel before/after?