又去健身館

在過去3週，我練習健身，原來我只可以舉20磅，現在可以舉50+磅，深蹲145 +磅，等等（其他方面也有提高），蠻開心喔（很開心）！

英文：For the past 3 weeks, I have been practicing weight lifting. Originally, I could only lift 20 pounds. Now, I can lift 50+ pounds, squat 145+ pounds, etc. I am very pleased!

又去健身館

在過去3週，我練習健身，原來我只可以舉20磅，現在可以舉50+磅，深蹲145 +磅，等等，蠻開心的喔！

This comma is redundant in Chinese.If you add the comma,this 等等changes its meaning to wait a minute.

I don't know the grammar of this kind of  的,but It is necessary for native speakers.

又去健身館房

在過去3週/個禮拜，我練習都有去健身，原來我只可以舉20磅，現在可以舉50+磅，深蹲145 +磅，等等，蠻開心喔！

英文：For the past 3 weeks, I have been practicing weight lifting. Originally, I could only lift 20 pounds. Now, I can lift 50+ pounds, squat 145+ pounds, etc. I am very pleased!excited.

又去健身館

在過去3週，我練習健身，原來我只可以舉20磅，現在可以舉50+磅，深蹲145 +磅，等等，蠻開心喔！

英文：For the past 3 weeks, I have been practicing weight lifting. Originally, I could only lift 20 pounds. Now, I can lift 50+ pounds, squat 145+ pounds, etc. I am very pleased!

過去3週我一直在健身，一開始我只能舉20磅，現在(進步到)可以舉50磅以上，以及負重深蹲145磅以上，這讓我感到非常開心！

又去健身館

在過去3週，我練習健身，原本來我只可以舉20磅，現在可以舉50+磅，深蹲145 +磅，等等，感到蠻開心的喔！

英文：For the past 3 weeks, I have been practicing weight lifting. Originally, I could only lift 20 pounds. Now, I can lift 50+ pounds, squat 145+ pounds, etc. I am very pleased!