I think you wanna say that your parents met each other for the first time in college ,and after a few months they got married ,so maybe you can say this sentence like this“我父母在大学的时候相互认识，几个月之后就结婚了。”

2.我妈妈是一个矮的又聪明又害羞的女人，我爸爸是一个高的又帅又幽默的男人。

In china,when we describe a person, we can use some conjunction like “但是”，“并且”，so you can say this sentence like this“我妈妈是一个聪明又幽默，但是有一点儿矮的女人；我爸爸是一个又高又帅，并且很幽默的男人。”

3.他们都一点儿也不一样。妈妈很努力却爸爸挺马虎。

you should change the order of some words like “他们一点儿都不一样”,but i don't know how long you have learnt Chinese,so i 'm not sure if you have learnt “反义词”or not,so maybe your teacher can tell you “努力”和“马虎” aren't “反义词”。

4.父母共同的生活非常快乐，他们已经二十六年结婚了。

the order of some words isn't correct.you can say like this“我的父母已经结婚二十六年了，他们的生活非常快乐。”

5.其实他们的爱情很浪漫，跟电影的一样。

You should add some words,“其实他们的爱情很浪漫，跟电影描写的一样。”

6.他们不仅接受彼此的缺点，而且觉得爱人的缺点很可爱。可能这是他们的爱情关键。

I should say this sentence is very good ,but you can make it better like“他们不仅能够接受彼此的缺点，而且觉得爱人的缺点很可爱。可能这是他们爱情的关键。

keep practicing and I think you can make great progress