(i.) Vocabulary.—
insilirent = in + salio = leap-on. And cf. our insult. Notice the usual phonetic change of vowel from a to i. (English derivatives will often help you to the meaning of a Latin word, though, for reasons that are explained to you in the Introduction, pp. 1, 2, § 4, you must let them lead you up to the root-meaning of the Latin word rather than to an exact translation.)
revellerent = re + vello = pluck-away. If you forget the meaning of vello, the supine vulsum through some English derivative—e.g. re-vulsion, con-vulsion—will probably help you to the root-meaning.
(ii.) Translation.—This sentence contains four finite verbs. As you read it through, underline the principal verb, clearly REPERTI SUNT, and bracket qui to vulnerarent. You cannot doubt which verbs to include in your bracket, for qui, which is a subordinate conjunction as well as a relative pronoun, serves as a sure signpost. Also revellerent and vulnerarent are joined by et—et to insilirent, so your bracket includes all from qui to vulnerarent. The commas in the passage will often help you to the beginning and end of a subordinate clause. Now begin with the principal verb REPERTI SUNT and its subject complures nostri MILITES, many of our soldiers were found.
qui . . . vulnerarent. This subordinate clause describes, just as an adjective does, the character of these complures nostri, so that qui = tales ut—i.e. brave enough to leap upon the phalanxes, and pluck away the shields (of the Germans) and wound them from above.
[IV.] Cum hostium acies a sinistro cornu pulsa atque in fugam conversa esset, a dextro cornu vehementer multitudine suorum nostram aciem premebant.
(i.) Vocabulary.—
ăcies = line of battle.
√ac = sharp (cf. ācer), perhaps thought of as the edge of a sword.
cornu = horn; so, figuratively, the wing of an army.