Language learning apps like Duolingo are useful, but they have their limits. Language teachers have told me that if students aren't making mistakes, they aren't learning enough. But that's an instructional tactic the teacher uses; adult language learners have to struggle beyond their abilities to gain language skills. LingodaAffordable and small online classes and tutoring. Lingoda specializes in online language learning in the form of small group classes and one-on-one classes, both held via video call.