1. Here is an alternative expression, "I moved my bed around and had to slice up the old mattress with a utility knife to throw it out—it turned out to be a real chore."

1. "Guidelines of" → "the guidelines in"
  Changed the capitalized "Guidelines" to lowercase "guidelines" as it's not a proper noun and added the definite article "the" before it to follow standard English article usage. Also, changed the preposition "of" to "in" as the correct preposition for referring to rules in a location is "in" rather than "of." This follows standard English prepositional usage for referring to regulations within a geographic area.

2. "have backache" → "have had a backache"
  Added the auxiliary verb "had" to create the present perfect tense "have had," which better indicates an ongoing condition that started in the past and continues to the present. Also added the indefinite article "a" before "backache" since "backache" is a countable noun in this context. In English, countable nouns require an article when used in the singular form.

3. Missing space after comma
  Added proper spacing after the comma in "recently, so" to maintain standard punctuation rules. In English, a space should follow a comma to ensure readability and proper formatting.

4. "I'd like" → "I wanted"
  Changed the modal "I'd like" (meaning "I would like") to the past tense "I wanted" to maintain proper tense consistency with the narrative of past events. Since the speaker is describing actions already taken (changing the mattress), the past tense more accurately reflects the completed action rather than expressing a current desire.

5. "Now that" → "And now"
  Replaced the incorrect usage of "Now that" with "And now." The phrase "Now that" is typically followed by a clause explaining a condition or reason (e.g., "Now that I have a new mattress, I can sleep well"), but in the original text, it wasn't used correctly. "And now" creates a proper transition to the current state resulting from the previous actions.

6. Removed "that"
  Removed the unnecessary conjunction "that" after "now" as it created an incorrect sentence structure. The phrase "now I can sleep well" is a complete independent clause that doesn't require the subordinating conjunction "that" in this context.

1. A hyphen was added between 'low' and 'rebound' to create a compound adjective. When two or more words act together as a single adjective before a noun, they are typically hyphenated.

1. Your expression is understandable but not fully natural in conversational English. The phrase "use it spaciously" is awkward and not idiomatic. Native speakers typically don't say they want to "use a bed spaciously."

More natural version:
  A. "I bought a semi-double size because I wanted a bit more space."
Or
  B. "I went with a semi-double so I could have more room to stretch out."

These versions sound more natural and convey the same idea in fluent, everyday English.

1. Your sentence was correct, but it's more natural to use "it is worth every yen."

2. The phrase "its great sleeping comfort" is understandable, but it's a bit awkward and not commonly used in natural English. Native speakers would usually phrase it differently.

So instead of:

"...because of its great sleeping comfort."

You could say:

"...because it's so comfortable to sleep on."

"...because of how well I sleep on it."

"...because it offers excellent comfort."