1. I don't know how to tie this ribbon.

-Don't worry. Let me help you with that.
(What is the meaning of 'with' in the last sentence? About?)

2. Why is that a problem?
- Im so nervous. I could forget everything.
(What is the meaning of 'could' here?)

3. I'll keep that in mind.
4. I'll bear that in mind.
5. I'll have that in mind.
(Are they all the same in meaning? Do you have some other similar expressions?)

1. "with" is just referring to the task of tying the ribbon. "Let me help you with that task." or "Let me help you do that task."

2. The verbs "could" and "would" and "should" are all verbs that indicate POSSIBILITY, not fact. "I'm so nervous that I might [could] forget everything." That's not a fact, but it's a possibility.

3 and 4 are fine, and each means the same as the other.

5 is different. To have something in mind means you're thinking about it or thinking of doing it.

1. In the sentence "Let me help you with that," the word 'with' is used to indicate the instrument or means by which the action of helping is carried out. In this case, 'with' implies that the help will be provided by using or employing some method or tool to assist in tying the ribbon.

2. In the sentence "I'm so nervous. I could forget everything," the word 'could' is used to express possibility or potential. It suggests that there is a chance or a likelihood that the speaker might forget everything due to their nerves. 'Could' is used here to indicate a hypothetical or uncertain situation.

3. "I'll keep that in mind," "I'll bear that in mind," and "I'll have that in mind" have similar meanings. They all convey the idea that the speaker will remember or consider the information or request that was mentioned. These expressions are often used to indicate that the speaker will take something into consideration or use it as a reference in the future. Some other similar expressions include:

- "I'll take note of that."
- "I'll make a mental note of that."
- "I'll remember that."
- "I'll put that on the back burner."
- "I'll store that away for later."
- "I'll keep that on file."
- "I'll hold onto that information."