五一 - wǔyī - 5-1 (May 1st)
节 - jié - festival / holiday
学生 - xuésheng - student
狂欢 - kuánghuān - party / carousal / hilarity
戴上 - dàishang - to put on (hat etc.)
白 - bái - white
帽 - mào - hat / cap
高兴 - gāoxìng - happy
跳进 - tiàojìn - to jump into
冰 - bīng - ice
湖 - hú - lake
欢庆 - huānqìng - to celebrate
春天 - chūntiān - spring (season)

Noun / Pronoun + 的 + Noun - Expressing a possessive particle with "Noun / Pronoun + de + Noun" (indicate a relationship of possessor / possession)
芬兰的五一节
很多芬兰人在这一天会戴上他们的小白帽，这是芬兰的学生帽。

Noun 1 + 是 + Noun 2 - Expressing that Noun 1 "is" Noun 2 with "Noun 1 + shì + Noun 2" (是 is only used to link two nouns, it cannot be used to link a noun and an adjective)
5月1日是五一节。
在芬兰，这一天是学生们狂欢的一天。
这是芬兰的学生帽。

Noun + 们 - Expressing the plural form of a noun with "Noun + men"
这一天是学生们狂欢的一天。

Phrase + 的 + Noun - Expressed to link a noun to a preceding phrase with "Phrase + de + Noun"
这一天是学生们狂欢的一天。
学生们都很高兴

Subject + 会 + Verb / Adverb - Expressing that sth "will" happen or that sb "will" do sth with "Subject + huì + Verb / Adverb"
很多芬兰人在这一天会戴上他们的小白帽
他们有的人会跳进冰湖里。

Verb + 上 - Expressing a movement "up or on" with "Verb + shàng"
很多芬兰人在这一天会戴上他们的小白帽

Subject + 都 + Verb Phrase - Expressing the action apples to "both / all" with "Subject + dōu + Verb Phrase"
学生们都很高兴
他们都在这一天欢庆春天来了。

Noun / Pronoun + 很 + Adj. - Expressing "very" or to link a noun or pronoun and an adjective with "Noun / Pronoun + hěn + Adj." (sometimes the 很 is translated as "very" but often it is a link between a noun and an adjective)
学生们都很高兴

有的… - Expressing "there are some…" with "yǒude…"
他们有的人会跳进冰湖里。

(在)...里 - Expressing "in / inside…" with "(zài)...lǐ"
他们有的人会跳进冰湖里。

New Situation + 了 - Expressing that there is a change of state or that the action has just happened "now" with "New Situation + le"
他们都在这一天欢庆春天来了。

芬兰 - Fēnlán - Finland