Hello!
I’ve noticed that there is used wrong grammar for obligation.
For example, in Japanese 2 level 23 there is a sentence: 私は傘を買わなくてはいけません which is translated into “I HAVE TO buy an umbrella”, but ~てはいけません means “must NOT”. Instead it should be 買わなければいけません (kawanakereba ikemasen), am I right?
And the 3rd course is full of sentences like this.