What is the purpose of "co" before the adverbs?
nejrychlejší = fastest (adjective)
nejrychleji = fastest,the fastest way (adverb)
co nejrychleji = as fast as possible
why not: do you want to now how? as it is in other sentences?
There are many acceptable translations using "Do you want to know how..." If you used it and your answer was rejected, we can't tell you why without seeing your complete answer.
I do not understand, suggest a complete translation.
chybí mi tam na výběr as takže nemůžu udělat správně :-(
Could you show a screenshot? We do not set theword bank tiles, you can file a bug report to Duolingo.