You're a Brit, so stop with the "local currency ... in my home country" Spy vs. Spy bullshit
Which is not to say you shouldn't drop the rest of the bullshit, you should. Because you would have done better with almost every actual investment option, including frickin' index funds.
TL;DR: Yes, you *were* doing it wrong. First because "with poor results - I'm not a trader," and later by thinking that money is an investment.
Sure, USD is nearly perfect money, but trust me -- an investment it is not

Which is not to say you shouldn't drop the rest of the bullshit, you should. Because you would have done better with almost every actual investment option, including frickin' index funds.
TL;DR: Yes, you *were* doing it wrong. First because "with poor results - I'm not a trader," and later by thinking that money is an investment.
Sure, USD is nearly perfect money, but trust me -- an investment it is not

The local currency wasn't GBP, nor was it my home country's currency. (My home country at the time wasn't Britain, either, but that's not the point). Incredibly, my brief foray into the carry trade wasn't my only investment at that time but thank you for your investment advice - many years too late, mind, but interesting all the same. Beyond that we're back to your narrow definition of invest. Let me put it like this...
An investment management firm has a "fixed income" section. Besides derivatives and bonds, what else do you think they invest their clients money in? And how do you think they acquire it?
You frighten me. Here's what an index fund is:
Quote from: www.investopedia.com/terms/i/indexfund.asp
An index fund is a type of mutual fund with a portfolio constructed to match or track the components of a market index, such as the Standard & Poor's 500 Index (S&P 500). An index mutual fund is said to provide broad market exposure, low operating expenses and low portfolio turnover.
So no, not "investing in money," if that's what you're thinking. Re. "home country":
You're a Brit, so stop with the "local currency ... in my home country" Spy vs. Spy bullshit

Yes, very good, we all know what an index fund is. But what does that to do with the questions I asked you? Equities and fixed income are two very different things.
I'm not going to tell you what countries I've lived in. It's really not relevant, and frankly it's a little creepy that you'd even care. If you need to have a more concrete example, lets say I'm a Armenian who now lives in Belgium but used to live in China, and while there was posted to Djibouti. But honestly - none of this is relevant. I thought personalising it might help you understand. Perhaps I was wrong - I'm doing my best to accommodate your foibles, honest!
You're not going to tell me what your "home country" is because, like most humans, you wish to keep your lying to a minimum.
And because you're going to spin fairy tales about making sound Forex investments [lol!] which, implausible as they may be, can not be proven false sans specifics

That said, I can offer you multiple cases Beanie Babies investors who beat actual IRL index funds. Please do not misconstrue that as advice to invest in Beanies.
Please don't be offended if you find this disclaimer patronizing -- past experience has taught me that everything here needs to be spelled out.
Re. fixed income [securities]: where did that come from? what do those have to do with anything I said?