@Pusokong
Makagawa ako nito... = I, to be able to make/do this...
Kailangan ang isang oras para makagawa ako nito. = An hour is needed so that I can/would be able to make/do this.
Nakagawa ako nito. = I was able to make/do this. or I was able to do/make something like this.
Nakagawa ako nito sa loob ng isang oras. = I was able to do/make this in an hour.
Nakagawa ako nito noong isang taon. = I was able to do/make something like this last year.
Nagawa ko ito. = I was able to do it/this. or I did it/this.
Magagawa ko ito. = I can do it/this.
Depending on the context, "nakagawa ako nito" and "nagawa ko ito" could mean the same thing. "Makagawa" is more often used with creating things, i.e., "to make", while "magawa" is usually just "to do".