What metodology does sololearn use?
Waterfall? Or Agile? Or Prototyping?
Most likely agile or similar to it. Definitely not waterfall since they're continually updating the website. With pure waterfall, no changes are made after releasing the product. They might have prototyped when the initial requirements were gathered but I doubt they would now. Not related to any of those methodologies but it seems like they test in production too much which leads to frequent bugs. I suspect they don't test changes locally or in a staging environment much if at all before releasing new changes to this website.