The topic is quite common, you can even say a hackneyed one. We will not "pour water" in vain and repeat what you can read on any site, at least somehow touching on the topic of money.
So, let's start with the fact that there is a fairly common view that the savings should be kept in parts in different currencies (as a rule, it is the currency of their country plus the euro and the dollar, or something like that). There are a lot of variations on this topic.
On the other hand, there is another opinion, also quite common. It consists in the fact that savings should be kept in the currency of the country in which you live.
Both of these opinions take place and have a number of grounds, so the adherents of both will be right. But only in part.
Let us not look here at these two approaches and their merits. Instead, we will go our separate ways.
Let's start with the amount of savings you have at the moment. If that's less than your monthly income, then it makes sense not to do anything and leave that money at home "under the barrel", so to speak. If you are afraid to spend it or just don't want it at home, then take it to the bank and put it in your national currency and keep it in your national currency.
If the amount of savings is more than two months' income, then it makes sense to take it to the bank just for better safety and security. The scheme is the same - a deposit in the national currency. Well, you can still make a currency deposit, just like that, play, warm your soul, so to speak.
I look forward to your questions, objections, and indignation. Let me explain all of the above.
First, the expediency of opening a currency deposit appears when the national currency begins to fall, devalue. Then you will be able to earn more on the exchange rate difference than on the interest on the deposit itself. When the situation in the country is more or less stable and the rate is more or less stable (the situation in the country will not always affect the rate), then the economic sense of the currency deposit is lost, because the interest and income on the currency deposit is always less than interest and income on deposits in the national currency.
Don't you believe it? Count for yourself. I won't give any examples, because everyone in their own country is in individual conditions. Take the amount in the national currency, choose the deposit in the national currency and calculate how much it will bring you income. Now take the same amount, convert it into foreign currency (dollar, euro or other), choose the currency deposit you like and count how much you earn. Approximately, with the same deposit equivalents, you will earn 1.5-2 times more on the deposit in the national currency than on the foreign currency deposit.
That's the whole arithmetic. Check and be surprised.
It's a different matter if you just want to keep your savings in foreign currency. Then please.
In general, it doesn't really matter which currency you keep your savings in for one simple reason. And this reason is the following - bank deposits are not a tool to earn money, but only the safety of your funds from different swindlers, from you and your desires, for the implementation of which you can recklessly spend your blood money. How to choose banks for savings you can learn from the article "Choosing a bank to open a deposit", and the nuances of choosing bank deposits are described in the article "Deposit deposits".
A bank deposit can only please you with a tangible profit if the amount of your deposit is about 100 times more than your monthly income. Then it will be interesting, and as long as it is not unfortunate, a deposit in the bank is a tool to save your savings until you decide to spend them.
That's basically the whole story about which currencies to keep your savings in. The main thing is to think with your head and before investing something - do not be lazy and consider whether it is worth it. The topic of investing money is described in detail in the article "Where to invest your money".