Q: young -> younger [youn-ger (G is in the second syllable)] と sing -> singer [sing-er (G is in the first syllable)] はどう違いますか?
A: singer の ng は、ch や th の仲間で、二つの文字で一つの音を表すものです。
ng の音は、国際音声記号では /ŋ/ と書きます。

younger は /jʌŋgɚ/ と、gの音も作って発音しますが、
singer は /siŋɚ/ と、gの音なく発音します。

それで gの子音で younger の ger が始まり、
siŋ だけの "sing" に er が加わったのが singer という感覚です。
(/ŋ/ で始まる音節は英語にないです。ベトナム語ならありますが。)
Q: young / strong -> younger / stronger と sing -> singer はどう違いますか?
A: Younger and stronger are used when you want to compare the strength or age of two things or people. For example:
- She is stronger than me
- My brother is younger than my sister
Sing is an action, but a singer is a person who sings.
Does this help?


Q: I seems like I became more younger この表現は自然ですか?
A: Your english is great but instead of "I seems like I became more younger" should be "It seems like I become younger"
Q: you are more younger than me この表現は自然ですか?
A: You are younger than me.
Q: it is important to get more younger to participate in these activities この表現は自然ですか?
A: get the younger to participate...
Q: A: You look more younger then I thought!
B: I took it as a compliment. この表現は自然ですか?
A: Change "more" to "much". Also "You look younger than I thought" works too.
"Then" should be spelled "than". "Then" is for time and "than" is for comparison.
Q: Nowadays, more and more younger people think that they can't live a day without a cell phone. この表現は自然ですか?
A: "Nowadays, more and more young people feel that they can't live a day without a cell phone." :)