A tortoise is accepted. Maybe "you" are not that slow as well ;)
We only have one word unless you are really into these animals and need to differentiate. I guess because of that, when a Polish person learns English they rather only learn "turtle".
To tell the truth there are many native English speakers who don't know this either.
whenever you feel like it. those two are equal.
but it is od+genitive; niż+nominative.
I suppose I should know this by now, but slow and free are the same word in Polish?
They may be, but "free" has more than one meaning, right? Let's just focus on the basic ones.
So "slow" is "wolny", true. Also "powolny", which is helpful if there's a threat that what you want to say may be ambiguous between 'slow' and 'free'.
"free" as in "freedom" is indeed "wolny". But than you also have what Wiktionary names "unconstrained", which is "swobodny". And finally, "free" as in "no paying" - this can be "bezpłatny" or "darmowy".
It is still rejecting 'tortoise' and I know it uses the same word. Reported.