The verb 'parlez' means you all speak, you all talk. The verb is in the second person plural ['vous'] of the present indicative tense. The second person singular is 'tu parles'.
(vous) parlez means (you) speak in French.
Parler means to talk
The statement 'Parlez en francais' means Speak in French. In the word-by-word translation, the verb 'parlez' means '[you] speak'. The preposition 'en' means 'in'. The noun 'francais' means 'French'.
parlez-vous français means 'do you speak French' in French.
The sentence 'Alors vous parlez francais' means So you speak French. In the word-by-word translation, the adverb 'alors' means 'in that case, so'. The personal pronoun 'vous' means 'you'. The verb 'parlez' means '[you] speak'. And the noun 'francais' means 'French'.
The question 'Est-ce que vous parlez Francais' means Do you speak French. In the word-by-word translation, the verb 'est' means '[he/she/it] is'. The demonstrative pronoun 'ce' means 'this'. The conjunction 'que' means 'that'. The personal pronoun 'vous' means 'you'. The verb 'parlez' means '[you] speak'. The noun 'Francais' means 'French'.
parlez plus fort means 'speak up' in French.
This is a question: "Do you speak French?"
The statement 'Parlez en francais' means Speak in French. In the word-by-word translation, the verb 'parlez' means '[you] speak'. The preposition 'en' means 'in'. The noun 'francais' means 'French'.
If that is an attempt at 'Parlez-vous francais' you might want to stick to english. :) Parlez-vous francais does mean 'Do you speak french?'
Parlez-vous le français means "do you speak French?". (note: French speakers are likely to often drop the 'le')
It is french and it means "do you understand/speak"