Learn Polish: Niech asystent osobiście przekaże wiadomość. - Let the assistant pass on the message personally.

The word niech is used to create third-person commands, translating to "let [someone] do [something]". You just take niech, add the subject (asystent), and use the regular 3rd-person singular form of the verb (przekaże).

The lesson says to use niech with a present tense verb. Isn't przekaże future tense?

Good eye! The rule is actually to use the basic conjugated form. For imperfective verbs, that is the present tense. But the verb used here, przekazać (to pass on), is perfective (it focuses on a completed result). Perfective verbs don't have a present tense, so we use its future tense form (przekaże - he will pass on). The grammar pattern stays exactly the same.

Wiadomość is the direct object being passed on. Why doesn't it have the feminine accusative ending -ę?

Because wiadomość is a special type of feminine noun. Most feminine nouns end in -a in their dictionary form and change to -ę when they are the direct object. However, wiadomość ends in a consonant. For feminine consonant-stem nouns, the accusative form looks exactly the same as the dictionary form.

How is the adverb osobiście (personally) formed?