In English, we would say “the more you practice, the better you will speak German.” In German, these types of parallel comparatives are called Proportionalsätze. Je + comparative adjective (phrase), desto or umso + comparative adjective (phrase).
“Je… desto/umso” is a type of two-part conjunction that is used to make comparisons and/or to make conditional or causal sentences. “desto” and “umso” are interchangeable. “Je” is always used first, and “desto/umso” is used second. The English equivalent is “the… the”. Both “je” and “desto/umso” must be followed by a comparative adjective.
1. Word order
A “je… desto” sentence consists of a main clause and a subordinate clause. The clause that begins with “je + comparative”, even though it always comes first, is the subordinate clause, which means that the verb goes to the end of the clause. The clause with “desto + comparative” is considered the main clause, but the word order still changes, as we place the comparative adjective or adverb in what could be considered position one, pushing the subject behind the verb.
2. Comparative and noun
A comparative can also be used in connection with a noun “mehr Geld” (more money), “mehr Zeit” (more time). The noun must be part of the “je + comparative” or “desto/umso + comparative” formula. “Je mehr Geld ich habe…” etc.
Examples:
Je mehr man arbeitet, desto/umso mehr Geld verdient man.
The more one works, the more money one earns.
Je länger ich schlafe, desto/umso müder bin ich.
The longer I sleep, the more tired I am.
Je öfter er übt, desto/umso besser wird er.
The more he practices, the better he becomes.
Let’s see an example to wrap our heads around this: Je weniger es gibt, desto höher wird der Preis sein. (The less there is, the higher the price will be.) Another form is je…umso, which means the same thing.