The currency is never the problem. Not having goods/services which are on par with other member states prevents internal trade. Not being able to devalue your currency prevents external trade. That creates debt which Germany and France buys and whoopdy doo, poverty and extremism.
The expansion of the euro into countries which aren't realistic trading partners is the problem but Germany and France love it, it means more long term wealth for them.
Latvia has exports, including to France and Germany, that means that there are goods that are on par or better. Devaluation does not solve anything long-term. What solves things is investment in high-added-value manufacturing and knowledge-based services. Or as you call those investments "buying dept".
There is no point for France and Germany to "buy [our] debts" if there is no expectation on our ability to repay those debts, likely from the new production.
You are confounding several things. It is NEVER cheaper to import than to fish, because importing costs money and fishing does not.
What you mean is that the opportunity cost of fishing is higher than its market value, meaning that there is another job that you can do for 8 hours that would make you more money than the fish that you could have caught in 8 hours would be worth. For that to be true, you need that job to exist that you can do, which is not always true in high unemployment situations.
And when that IS true, then it is a good thing, because that means that the economy as a whole is working more efficiently - you are not spending your time doing useless things, you do something more productive instead.
The expansion of the euro into countries which aren't realistic trading partners is the problem but Germany and France love it, it means more long term wealth for them.