I'd be a bit cautious about trying to say the tenses of Swahili are exactly equivalent to the tenses of English. As far as I've seen, the simply -a- tense is used much less often in Swahili than the simple present tense is in English. The -na- tense is often equivalent to the present continuous in English, but not always.
In the Turkish course, they are very strict with equating the -er- tense with the present simple of English and the -iyor- tense with the present continuous ... and then people completely lose their minds in the comments when it doesn't match up exactly, for example when "I love you" has the -iyor- tense, people complain that it should accept "I am loving you" even though that's unnatural English.
Also ... this course doesn't teach the -a- (aorist) tense at all :-/
I agree with you that only in one point that when you translate one language to another sometimes one tense in one language is translated as another tense in another language. I have no objection to that but that does not mean the equivalent tense does not exist, the tense may exist even if it is not commonly used.
In Swahili for example we have the following tenses:
Sisi twaimba wimbo wa Taifa kila siku shuleni.
Sisi huimba wimbo wa Taifa kila siku shuleni
Sisi tunaimba wimbo wa Taifa shuleni.
Can you say these sentences above do not exist in Swahili? You are wrong. These sentences do exist in Swahili and the point here is not only about being equivalent to English or not but what are they?
The first two sentences number 1 and 2 are Simple Present Tenses because they talk about the action of singing is done every day and the structure uses tense marker ‘a’ before a verb just like 'do or does' used before a verb in English. Another simple present tense is used by prefixing ‘hu’ before a verb but this time without subject marker -tu from Swahili Subject Pronoun sisi.
The sentence number 3 is Present Continuous Tense.
Do not say the tenses do not exist although you can simplify your translations by choosing the Simple Present Tense of another language in place of Present Continuous Tense of another language.
George Mwidima Kihanda.