This new tongue would be sSpanish, since it shares a lot of similarities with Portuguese.

But I think that Iit would be better to focus on English untill be at I reach a fluent level before jumping into Spanish, so that it would not undermine my progress in English.

I'm aware that many have started learning another language even though they haven't reached high proficiency at the previous target language.

In addition to that, some people claim that once you've become able to communicate in a certain tongue you probably should be more skilled to pick up another one.

Therefore, I've been postponing on the decision of diving into a new language, in spite of my desire of speaking with Mexicans friends without relying on English.

This new tolanguage would be sSpanish, since it shares a lot of similarities with Portuguese.

although "tongue" is technically correct, it sounds odd and is rarely used in anything but a formal context.

But I still think that I better focus on English untill be at a fluent level I reach fluency before jumping into Spanish, so that it would not undermine my progress in English.

I'm aware that many have started learning another language even though they haven't reached a high proficiency atin their previous target language.

In aAddition to thatally, some people claim that once you've become able to communicate in a certain tongue yousecond language, you will probably should be more skilled ato picking up another one.

Therefore, I've been postponing on the decision tof divinge into a new language, in despite of my desire tof speaking with Mexicans friends without relying on English.

In addition to that, some people claim that once you've become ablelearned to communicate in a certain tongue, you probably should be more skilled enough to pick up another one.

I think "become able to" sounds awkward even though it's grammatically correct. I would use "learned to" or "are able to" instead.

You could say "more skilled at picking up" or "skilled enough to pick up".

When is it the right moment to start learning a third language?

This sounds slightly better to me, although I don't think the original was wrong per se.

This new tongue would be sSpanish, since it shares a lot of similarities with Portuguese.

But I still think that I better focus on English untill be I am at a fluent level before jumping into Spanish, so that it would not undermine my progress in English.

I'm aware that many have started learning another language even though they haven't reached a high level of proficiency atin the previous target language.

In addition to that, some people claim that once you've become able to communicate in a certain tolangueage, you probably should be more skilled ato picking up another one.

Therefore, I've been postponing on the decision tof divinge into a new language, in spite of my desire tof speaking with Mexicans friends without relying on English.

This new tongue would be sSpanish, since it shares a lot of similarities with Portuguese.

It's very minor, but the comma isn't necessary.

But I still think that I better focus on English untill be I'm at a fluent level before jumping into Spanish, so that it would not undermine my progress in English.

I'm aware that many have started learning another language even though they haven't reached a high proficiency atwith the previous target language.

In addition to that, some people claim that once you've become able to communicate in a certain tongue, you probably shwould be more skilled to pick up another one.

Therefore, I've been postponing on the decision of diving into a new language, in spite of my desire tof speaking with Mexicans friends without relying on English.