The OP has used mean "could" to mean "was able to". I agree "was able to" would have sounded more natural in those sentences.So I'd expect "I was able to top up ...", am I not right?
It isn't really. Some people like to look tanned, but when they have a nice tan and then stay out of the sun for several days or weeks, their tan will fade, they will grow paler, and will feel the need to refresh it or top it up.I find the use of "top up" in relation to a tan odd.
I would not recommend it. See other comments about "at last" being probably better than "finally", and "was able to" being better than "could".Can I say "Finally I could fix my computer"?