To stress what a sentence is about, move that part to the front. Then the rest of the sentence carries on in its normal order. Fronting needs something to push against: you use it when you are singling this thing out from another one, stated or understood. The cake I liked, but not the coffee works because of the contrast. A bare That book I've already read, with nothing to set it against, sounds odd.
Move the object to the front
I can solve this problem. → This problem I can solve.
I've already read that book. → That book I've already read.
I have money, but I don't have time. → Money I have, but time I don't.
Try it: I really liked the cake, but not the coffee. Stress the cake by moving it to the front. (Leave out the word you don't need.) Answer: The cake I really liked, but not the coffee. — Move the part you're stressing to the front, then keep the normal order: The cake I really liked, but not the coffee. The contrast ("but not the coffee") is what makes fronting sound natural — it points at the thing you're singling out. "Did I" would swap the order like a question, but fronting keeps it normal, so leave it out.
Don't swap the order after it
This is the trap: after the fronted part, the person and verb stay in their normal order. Don't turn it into a question.
I can solve this problem. → This problem I can solve. (not "can I solve")
She never makes those mistakes. → Those mistakes she never makes. (not "does she make")
He always tells the truth. → The truth he always tells. (not "does he tell")
Not "This problem can I solve." — say "This problem I can solve.". After the fronted part, keep normal order: I can, not "can I".
Try it: I have already sent the report. Front the report, but keep the normal order after it. (Leave out the word you don't need.) Answer: That report I have already sent. — After the fronted part, the person and verb stay in normal order: That report I have already sent. "Have I" swaps the order like a question, which fronting doesn't do, so leave it out.
I DO understand (stress with do)
To insist that something really is true — often when someone doubts it — put do, does, or did before the base verb. That extra word carries the stress. Use do/does for the present (does with he/she/it) and did for the past; the main verb stays in its base form, never the past participle.
"You don't care." → "I do care."
She rarely calls, but she does call on my birthday. (not "does calls")
You think I forgot? I did remember. (not "did remembered")
Not "She did called me." — say "She did call me.". After do/does/did, the verb stays in its base form: did call, not "did called".
Try it: Someone doubts that you understand. You want to insist. Add do to show you really mean it. (Leave out the word you don't need.) Answer: I do understand your concerns. — To insist on a plain present idea, put do before the base verb: I do understand. Once do is there, the verb stays plain: understand, not understood. "Understood" would change the time and double the work do is already doing, so leave it out.