Hot answers tagged word-choice
First you were right by using 什么 to mean "something" in Chinese. However, 了 is a past tense indicator, which was not supposed to be there because you didn't hang out yet. The correct way to say “Do something together” in Chinese is: 一起做些什么 or 一起做点什么
if by 无用 you mean useless and by one word you mean one character then I would recommend: 废 it has a lot of meanings but specifically here it contains the meaning: waste; useless; disused; superfluous in ²fèizhǐ -ABC
It depends why that thing is considered "無用". For example, if it is considered redundant, you can say "贅".
In addition to @songyuanyao's extensive list, there's a surprisingly large number of sayings that are specifically about succeeding by persevering: 勤能補拙 日起有功 累足成步 跛鱉千里 駑馬十駕 功在不舍 跬步千里 事在人為 有志者事竟成 精誠所至，金石為開 一分耕耘，一分收穫 皇天不負苦心人 人一己百 九轉功成 艱難玉成 In the question's specific context, I would say the first would be the best choice (我的发音还差得远，可是勤能补拙). But 2-5 can ...
By no meaning of bad,among the friends you can say:"混"or"泡" “在朋友家混”,"hang out in friend's place" “在酒吧混”or“泡吧”,"hang out in the bar" “我们今天去泡游泳池”，"We are going to hang out in the pool" "晃悠"also express "hang out" “他和朋友在广场晃悠”，"He is hanging out with friends in the square." When you invite friends on the phone,you can say:“今天出来晃晃？”，or“出来兜兜？”
Why don't you say "一起去玩" / "一起去走走" / etc.? There is no need to stress the phrase "doing something" in this case.
只要功夫深，铁杵磨成针 is good, and also: 坚持不懈 锲而不舍 水滴石穿 百炼成钢 熟能生巧 精卫填海 卧薪尝胆 有志竟成
凤毛麟角 is used when somebody has some special skills or talent which is very rare. When you are trying to compliment someone(really has unique skills), it's a good phrase.
很多美国人都想去中国，但会说或写中文的人却是凤毛麟角 There are many Americans who want to go to China, but few can write or speak Chinese.
As Wang Fei probably would say: 执迷不悔
I think most Chinese people would express this with a simple "慢慢来," which pretty much includes all the elements you're looking for ("I know I have a long way to go, but if I keep trying, I can succeed."). If you want something more idiomatic, consider: 一口吃不成胖子 ABC 1 Nothing can be accomplished in one single effort. 2 Rome wasn't built in a day. ...
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