To me, motivation is the most important consideration. Compared to motivation, all other keys, such as a person's age or resources, shrink to insignificance. Having said that, language is culture, and one should not choose a culture one dislikes for some reason.

Consider why you want to learn a language and for what purpose.if your heritage is important to you, surely that answers your own question - learn the language of your heritage. Learning for pleasure, I would chose whichever language I think looks or sounds nicest. As an aside, just because you mentioned it, I am learning Mandarin Chinese and I think there are a lot of misconceptions about how difficult it is. Actually it's not that hard, it's very different to what I'm familiar with seeing (Chinese characters vs ABC's) which makes it appear an incredibly daunting task at first, but structurally and grammatically it's easy. There are no verb conjugates, for example, and tenses are far easier than learning French or German. Granted, some aspects are quite difficult, but it's credibly satisfying to conquer each challenge. Mandarin Chinese is broadly spoken, particularly by the younger generations and it is quite standard. Cantonese is a dialect mostly spoken in and around Guandong, Hong Kong, etc. Whatever language you chose, if you don't enjoy it after giving it a good try then just start another one.

I can see how confusing you are, so try to learn one of the Official languages of the United Nations: Arabic (Literary Arabic) Chinese (Standard Chinese, Simplified Chinese characters) English (British spelling) French Russian Spanish