Basic/cheap English grammar lessons for non native English speakers never teach you anything about singular “they”.

Honestly, not all that surprising. In many cases where you wouldn’t necessarily know the gender, its when referring to someone by their profession. For example, if you were referring to the person who brought your mail to remark upon the poor handling of a package, you might simply say the mail carrier didn’t treat this with care, instead of they didn’t treat this with care. The vast majority of native English speakers probably use the singular they in passing, but I would be surprised if it’s more often than a few times per month.

How sad, cause then one who tries to write/speak as best as possible, might not be correct because of how they got to learn a bit of English.

For what it’s worth you’re doing a wonderful job. Another strategy that I see less often, but am pointing out because you just used the word, is de-gendering language by using indefinite articles, such as ‘one’. Glad to know I’m not the only person who sometimes uses English in this fashion.

I know this will sound as blasphemy, but what I’ve read from Skakespeare, I’ve did in Castellano, hehe, so I wouldn’t notice what you mentioned. Good to know.

I would be more surprised if you didn’t read Shakespeare in your native language and I certainly don’t think it’s blasphemy. I’ve read plenty of famous works that were translated to English. We don’t all have time to respect it in its natural form, more so if it’s constructed with archaic grammar and full of words long since abandoned. Most of the Shakespeare I read in school wasn’t in the original form either, and had at least some amount of restructured words and grammar.