I can't fully understand what you mean

I can't fully understand what you mean
我不能完全明白你的意思,我翻译成I can't fully understand what you mean,can't fully understand 的表达是否正确,我看别人都是这么翻译的：I could not fully understand what you mean 和 I do not fully understand what you mean ,我是自学英语的好多知识都不懂.