In this sentence: "Sie sollten öfter schwimmen gehen." "You should go swimming more often."
Why is this "sollten" and not "sollen". Duo is doing this in every sentence that uses this verb, and I don't get it.
Verbformen tells me "sollten" is the imperfect, past tense form, and I see nothing past tense about this sentence. It is telling someone what they "should" be doing from now on, which is at least present or future tense in my mind.