You're absolutely right to question this sentence! The verbs "contribute" and "devote" are used incorrectly here. It's better to say: "...and I will do my best to contribute and devote myself to the people and the country until the last day of my life." OR "...and I will devote myself to the people and the country and contribute all I can until the last day of my life." Good luck

"Myself" is a pronoun that works just like "me", so just as you cannot say "all me", you also cannot say "all myself". You need to say "all of myself". To fix the idea in your mind, listen to the song "All of Me" sung, for example, by Billie Holiday. It is not wrong to "contribute yourself", but we don't usually say that. More often, we specify more precisely what it is about yourself that you are contributing: "I contribute my time, or money, or skills to this cause" In an extreme case, where you actually did want to contribute all of yourself, you could "contribute your life". But that is quite strong. It makes you sound like a soldier who expects to die, or a monk who is entering a monastery. It is easier to use "devote". Saying that you "devote yourself to a cause" is quite reasonable. It does not sound extreme. It does not sound like you are sacrificing yourself. It only means that you feel a strong commitment. The first part of the sentence is badly constructed: "But no matter....all my best" contains oodles of errors.

This is probably better as two sentences rather than one. But the devote and contribute part should be... I will devote myself to the people and contribute to the country. You can't contribute to people. A contribution is something you give or offer up as part of a larger thing or organisation. So you can contribute to a charity for example. Or you can contribute to GoFundMe page. If we are talking about people we usually say 'donate' or assist.