a medical question about dementia?

Altho it could be, it sounds like something you should explore in other areas, ie, too many changes, a different culture, different food, (do you have food allergies) , hormones imbalanced,diabetes, etc.....

If you have concerns for alzheimers or something like that, have an MRI done of your brain, or even a functional MRI...

If you can get your hormones checked, thyroid, sex,adrenal, cortisol and balanced...

That will relieve you of the most obvious, here are some sites for you to check out

Dementia is doubtful. Is your current location new to you? You may be having to adjust to too many new things at once and your mind is in overload status. You are fearful and that sometimes freezes us up in the memory department. If you are frightened or constantly worried that you may not be in the right place, get to places on time, worried about meeting new people, not making cultural mistakes, your brain just can't work fast enough to retrieve recent past info.

Chill a little bit. You will be fine when you are more comfortable.

Is it possible what you are describing is state dependent learning?

Certain chemicals such as caffiene / nicotine when withdrawn can seem like you've lost "knowledge" when in fact you haven't, your brain may have to 'repath" to learned knowledge through non-state pathways.

dementia, not likely, hormones not likely, memory loss not likely..

writing in a learned behavior as is general knowledge. these are rote issues related to recall.. My take would be simple brain exercise, say for example, to pull out a game of "Trivial Pursuit", pull out each card and read the question and answer them.. See if you regain something you think you've lost. You might be surprise, it's been there all along.