对 as "to treat" - (A 对 B + adj) - 4 sentences

我对学习汉语真的很热情。
(I'm really enthusiastic about learning Chinese.)

一些训狗师们对他们的狗不好（It would be better if you replace 好 with 友善）。
(Some dog trainers are not kind to their dogs.)

如果你对跳舞太严重把跳舞看得太重，可能你就会忘记怎么享受它。
(If you treat dancing too seriously, you might forget how to enjoy it.)

我的狗觉得狗敏捷（我们一起做的运动）是她的工作，她对它很严重很认真地对待它。
(My dog thinks Dog Agility (sport we do together) is her job and she treats it very seriously.)

对 as "to treat" - (A 对 B + adj) - 4 sentences

我对学习汉语真的很热情。
(I'm really enthusiastic about learning Chinese.)

一些训狗师们对他们的狗不好。 correct
(Some dog trainers are not kind to their dogs.)

如果你对待跳舞太过于认真严重，可能你就会忘记如何去享受它怎么有好玩。
(If you treat dancing too seriously, you might forget how to enjoy it.)

我的狗觉得狗敏捷（我们一起做的运动）是她的工作，她对待它很认真严重。
(My dog thinks Dog Agility (sport we do together) is her job and she treats it very seriously.)

对 as "to treat" - (A 对 B + adj) - 4 sentences

我对学习汉语真的很热情。
(I'm really enthusiastic about learning Chinese.)

一些训狗师们对他们的狗不好。 可以说 一些训狗师不善待他们的狗。
(Some dog trainers are not kind to their dogs.)

如果你太认真地跳舞，你可能忘记去享受它。 

(If you treat dancing too seriously, you might forget how to enjoy it.)

我的狗觉得狗的敏捷性（我们一起做的运动）是她的工作，她对它很认真。
(My dog thinks Dog Agility (sport we do together) is her job and she treats it very seriously.)

我对学习汉语真的热情。
(I'm really enthusiastic about learning Chinese.) 

---我对学习汉语真的很有热情。

如果你对跳舞太严重，可能你就会忘记怎么有好玩。

----如果你对跳舞太认真（可以替换成“执着”，“看重”等）的话，你可能就会忘记什么是快乐。

我的狗觉得狗敏捷（我们一起做的运动）是她的工作，她对它很严重很认真地对待它。
(My dog thinks Dog Agility (sport we do together) is her job and she treats it very seriously.)

I can't understand what does it means,but i guess:我的狗认为敏捷（灵活）是它（In chinese,people called animal 它 in normal,not 她.In the context of certain,can called "她"，if we called "她"，就是代表对它的一种敬意（with respect）.）的工作，它很认真的对待它。