Here are the corrections needed for each sentence:

51. **furnitures** → should be **furniture** (furniture is uncountable).
52. **exciting** → should be **excited** (to describe the children’s feelings).
53. **understood** → should be **understand** (to match the verb form).
54. No correction needed.
55. **deliciously** → should be **delicious** (to describe the taste of the pancakes).

So, the words or phrases that need correction are:
- 51: furnitures
- 52: exciting
- 53: understood
- 55: deliciously