Language learning apps are deliberately designed to be slow and ineffective to make you use them longer and thus give the company more money.
It’s designed to make you feel like you’re learning something, when in actuality you’re being lead on for months while you get ads shoved down your throat. If you actually felt comfortable in your ability to speak a second language, you wouldn’t be using the service. This is why the free market can’t be trusted. Its not in a companies best interest to actually teach you anything.