All your sentences make sence but not as same as your English sentences. All your "努力“ should be changed into "试图". 努力 basically means keep trying to do something, try very hard to do something,try it again and again,emphasizes that they've made a lot of effort to do it. 努力 as a noun means effort ：他多年的努力终于得到了回报。 Finally his years of hardwork paid off. as a verb. meaning make a great deal of effort on doing something 我一定会努力去做的。 Believe me.I will spare no effort to do it. as a adj. means industrious 她是个很努力的学生。She is a student with industy. as a adv. means 蜗牛正在努力地往上爬。 The snail is trying hard to climb upwards.

我在努力地理解你说的话，请说慢一点。 I am trying to understand you. Please speak a little slower. 我努力地学习汉语，但是汉语太复杂了。 I tried to learn Chinese but it is really complicated. 他努力地想要去爱他的妻子，但是他做不到。 He tried to love he wife but he couldn’t. 她在努力学习游泳。 She is trying to learn to swim. I think there is no big problems in your Chinese sentences. but just for the use of 了。It can be use for the meaning of the past time, but usully we put it after a verb or a adjective, expressing that something somebody have already done. e.g.: 我做完作业了。I have finished my homwork. 我从北京回来了。I have been back from Beijing. 我很努力地学习了魔术，但是依然做不好。I learned magic tricks very hard, but still can not do it well.

“努力”means:someone spend time or energy and so on that try to finsh something. Please correct my Chinese. 我在努力理解你的。请说慢一点。 我正尝试理解你，请说慢点。 I am trying to understand you. Please speak a little slower. 我努力了学习汉语， 但是汉语太复杂了。我尝试着学好汉语，但是汉语实在很复杂。 I tried to learn Chinese but it is really complicated. 他努力了爱他妻子，但是他不可以了。 他尝试着去爱他的妻子，但是他做不到。 He tried to love he wife but he couldn’t. 她在努力学习游泳。 She is trying to learn to swim. good job come on

“努力”means:someone spend time or energy and so on that try to finsh something. Please correct my Chinese. 我在努力理解你的。请说慢一点。 我正尝试理解你，请说慢点。 I am trying to understand you. Please speak a little slower. 我努力了学习汉语， 但是汉语太复杂了。 I tried to learn Chinese but it is really complicated. 他努力了爱他妻子，但是他不可以了。 He tried to love he wife but he couldn’t. 她在努力学习游泳。 She is trying to learn to swim. good job come on.

我试着打开这个网站，但是我努力了很多次，没有成功