After "day", you can put a period/stop there. You can make "It's just boring" a separate sentence or join the two sentences together with a semicolon (;). Your sentence about waiting all day was very good. It shows that you understand verb concept here.
Here are two examples for you:
Example 1: "I have been waiting for you here all day. It's just boring."
OR
Example 2: "I have been waiting for you here all day; it's just boring."
Replies
I have been thinking about It whole the day..
It has been raining for 2 hours.
What have you been doing since morning?
We have been invited to a marriage ceremony... ( Is this one correct?)
After "day", you can put a period/stop there. You can make "It's just boring" a separate sentence or join the two sentences together with a semicolon (;). Your sentence about waiting all day was very good. It shows that you understand verb concept here.
Here are two examples for you:
Example 1: "I have been waiting for you here all day. It's just boring."
OR
Example 2: "I have been waiting for you here all day; it's just boring."