The part of the sentence 'I can completely understand' is correct and usable in written English. You can use it when you are agreeing with someone or when you fully comprehend something that someone has said or explained. Example sentence: I can completely understand why you feel that way.
I can completely understand why this happens.
And I can completely understand that.
"I can completely understand saving money," she said.
And I can completely understand why I'm virtually alone.
But, he added, "I can completely understand how traumatized Ueli must've felt".
"I can completely understand why some artists want to pursue other models of learning".
"It's been amazing to have someone I can be really honest with, especially when I'm stressed with final year – she can completely understand".
By this finding, bearing designers can completely understand these instability phenomena existing in fluid-handling machines.
"She is a special case, and you can completely understand why she did it," said Dr. Susan Love, the author of a best-seller, "Dr. Susan Love's Breast Book," and a breast surgeon.
Because Shannon Parker has created this set of circumstances where you believe everything that is happening; where you see what it's like to be in that relationship from the outside, and at the same time, you can completely understand why everything that happens in that relationship is happening.
"There's a lot of desperation out there from fans to qualify and you can completely understand that.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union