You definitely shouldn't The point is that you have corrected your mistake yourself, without my assistance - one indeed gets the knowledge of "words, language structures, and concepts"© but not of the language itself. No matter how person learns the language, after all he/she knows not the language, he/she knows how to speak it. To sum up, you have two possible variants: "I speak English" and "I know how to speak English". Both variants are correct grammatically and under the matter of word usage, the second one though is of rude style, no native speaker would ever use that phrase.
You see, two higher education in linguistics, BEC Higher and continuous communication with native speakers (speakers of fine dictionary English, not broken or pigeon) allows me to be dead sure of the ostensible truth of my statement
Besides it's one of the frequent questions in various English tests on word usage, for example:
Fill in the gaps choosing the words from the list below. There is only one variant correct for every sentence:
My sister have been learning German since she was 10, now she ... it pretty well.
1) says
2) knows
3) speaks
4) tells
Hopefully now it's needless to tell you that the only correct variant here is #3
Anyway lectures of such themes are of little interest for other posters who come here to converse with each other. Therefore I suggest using private message inbox in case you have any further questions

Ляська, bloodygirl, people speak languages, not know. You can say it in Russian in this way - я знаю английский - but using this verb in English sentence relating to competence in languages is completely incorrect.
patricia, "18 goes into
54 a lot more times than 54 goes into 18" - the stark reality of life