I didn't attend to any training class but learned it on my own.

I didn't attend to any training class but learned it on my own.
I didn't attend to any training class but learned it on my own.

I didn't attend to any training class but learned it on my own.
把to去掉,attend直接可以加名词.

我没有参加任何训练班但却自己学会了

我没有参加过什么培训课程，都是靠自己学的。

attend to->attend
attend 是及物动词"参加"

我没参加任何训练课程就自己学会了。
这里是“not...but...”的句型