This is an interesting question. Language development is a fascinating topic!
There are two types of language learning:
1. Learning a natural language (a language that is learned without any conscious effort)
2. Learning a second-language
Nearly all babies learn a natural language and some may learn more than one (they are what we call, bilingual babies).
There are some critical periods for learning any languages and these vary depending on the aspects of language one looks at (syntax, semantics, etc...). (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3451048/)
Recent research shows that the approximate critical period for learning a second language appears to be at around 17 years old. (https://www.sciencedirect.com/science/article/pii/S0010027718300994) This does NOT mean that you will not be able to learn a second language after this, simply that it will be harder. Hence why it might have been easier for you to learn English at 8 years-old.
Now, depending on what languages you speak, it might be easier to learn some languages rather than others. For example, French and Spanish have very similar rhythms, phonemes, and are both romance languages, which would make it easier to learn one or the other, as long as you were fluent in one of them. However, it would be much harder for an English or French speaking person to learn Mandarin, because this tonal language is so different on many different aspects (for one, there are phonemes to which speakers of non-tonal languages are not sensitive, meaning that they cannot tell the difference between them). So yes, sometimes a language can be easy to learn, but at other times, it becomes much more complicated than having to learn a computer language.
As for being better at learning languages because you are bilingual, that is a possibility, but again, within the limits mentioned above of the language you decide to learn. Someone who knows French and Spanish may find it very easy to learn Italian, but still extremely hard to learn Cantonese. (https://www.psychologytoday.com/us/blog/life-bilingual/201506/can-second-language-help-you-learn-third)
Finally, psychologists do not agree on whether or not we have 'certain capabilities'. Many argue that anybody can become anything with the proper training and experience. Sure, as we grow, we become better in certain things, but you may find that by overcoming your preconceived ideas about yourself (ex: you are not good at learning computer languages), you can learn new things! I recommend reading Peak by Anders Ericsson. In his book, he really highlights how all the 'experts' were not born with special talents, but learned everything thanks to deliberate practice.