What is the best country for quality of life in Europe?

I am So happy for you. I would say  firstly Portugal would be easier.  Portugal has friendly people , good weather and good food and it’s somewhat cheap, however; Portugal  is still dealing with a weak economy .. and it’s hard to find different opportunities same as Spain however Spain seems so be quite popular almost expats. It’s up to your values! If you value more economic growth and more opportunity then try Germany, Netherlands,Austria,Switzerland ( but keep in mind it’s Switz is  expensive ). There is also England and Spain. 

This depends as much on your temprament as the country itself, you know?  For example, I am comfortable with high taxes as long as I feel that those taxes uphold my quality of life, but there are other considerations too.

I have lived in the United States and there were parts I really like and parts I really did not find any affinity with, but overall it was not a place I wanted to grow old.  I have lived in three Scandinavian countries and could imagine living in Denmark and would not mind SE Finland, but I really did not get on with the Swedish outlook on the world which I found strangely passive and smug at the same time.  There are parts of Germany I feel like I could slot right into, but other regions where I would always feel like an outsider, ditto for France, but I know that I could never settle in Italy or Greece, I just wouldn't fit in and I DO want to meld into my surroundings.  I feel comfortable in Estonia, not at all in Poland.  I don't know enough about the other A8 countries but wouldn't rule out dipping my toes.

As you can see, my OPINIONS are a personal jumble.  You need to ask the advice of someone who knows you well.  What are you like?  Do you need to be around people?  How would you fare in a non-tactile country where people visibly flinch if you stand too close to them (and they converse standing over a meter apart)?  Are you willing to relearn all the social rules or do you imagine being more of a lone wolf?  Are you an urbanite?  Is it important to you that there's a culture of being out in nature and therefore there is ample access to nature or does that not matter?  What is your attitude to transport?  How would you feel about living somewhere where people look down on non-car drivers and drive very short distances just to show off their flashy cars?

If you are looking to settle do you want to have children in the future?  If you do start thinking now about how children are brought up in your target country.  Don't underestimate how strongly conflicted you might feel about not giving your children a version of "your" childhood and losing the bond of common practices, not to mention needing to grit your teeth over cultural norms that seem wrong or even dangerous to you.  This can be really unsettling when attempting to parent in another country.

People often say the Scandinavian countries but they are taxed very highly and have brutal winters . If it’s so good why do they have such high suicide rates?

Judging by the desperation for people to get there, it must be England.

the happiest populations are found in places like Norway, Denmark and Switzerland, but it probably depends on what languages you speak

You're still going to need to get yourself a residency permit and possibly a work permit, but you won't need a visa and you can easily find out more at the Embassy for the country you eventually choose. 

If you already have Portuguese citizenship, why not Portugal? It's a wonderful country. 

france atleast you can make money with what you got

The best country in Europe (based solely on quality of life) is Germany. Other great countries in that regard are England, France, Sweden and the Netherlands. There are countries like Estonia and Portugal that are booming, but the problem is that if you leave the capital, the quality of life drops.

On the other hand, I understand that you have the possibility of working online, but I leave you an article that I read the other day that shows you the best cities to work in Europe. It was something that was interesting to me (I was not expecting the cities that make up the index) and I leave it to you because I think that a decision as important as moving deserves that you take into account all the factors.

https://www.filtrip.travel/post/the-best-cities-to...

Have you researched the work visa requirements? You can't move without one.

Also; if you want to move to Germany, you'll need to speak German. Do you?

If you only speak English, then you're limited to English speaking countries. 

Germany, Switzerland, Holland; or even Portugal, if you want a warmer climate.

Denmark. 

But you need to consider other things, like culture, weather, language, etc. 

Germany is fine if you already like it and speak the language.