Few questions about openings

Hi! I'm a beginner trying to learn chess, but I'm having problems with openings. I would appreciate if more experienced players could give me some advice. My rating at the moment is 1099 (highest is 1126) in classical. I only play classical 15+15 at the moment.

Here are some questions I have:
1) Which pawn opening (as a white) is considered better for a beginner to grasp: d4 or e4? I usually open with d4 and after that e3 to protect the first pawn. Is there something wrong with this opening?

2) What opening would be best to learn as a beginner? When I'm black and opponent plays e4 I usually respond with sicilian and as a white I use the opening described above.

3) Do you usually use the same opening when playing seriously or do you change it often?

4) Lets take the queen's gambit for example. What if someone responds to it with a pawn in c5? What can I do then? Capturing would lead to losing center control right? The question is what can you do when opponent doesn't react in an expected way? Do you just cut your losses and continue with another plan?

1) play 1.e4 as white, you'll get more open positions and you'll be able to practice tactics everytime
2) play 1.e5 against e4 and 1.d5 against d4. Playing classical opening will make it easier to understand how chess should be played.
4)If you have a plan and your opponent does nothing to stop it, simple continue with your plan.

"1) Which pawn opening (as a white) is considered better for a beginner to grasp: d4 or e4?"
I recommend 1 e4 to beginners, but 1 d4 is good as well, it does not really matter.
"I usually open with d4 and after that e3 to protect the first pawn. Is there something wrong with this opening?"
No it is a good opening, called Colle. World Champion Magnus Carlsen has played it occasionally. Edgar Colle played many briljant games with it.

2) "What opening would be best to learn as a beginner? When I'm black and opponent plays e4 I usually respond with sicilian and as a white I use the opening described above."
Sicilian Defence is good.

3) "Do you usually use the same opening when playing seriously or do you change it often?"
Best is to play the same opening all the time and in all time controls. That deepens the understanding of the resulting positions.

4) "Lets take the queen's gambit for example. What if someone responds to it with a pawn in c5?"
No problem, you think and you search for a good move.
"What can I do then?"
Usually push d5
"Capturing would lead to losing center control right?"
Yes usually, but there are exceptions.
"The question is what can you do when opponent doesn't react in an expected way?"
Think and find a good move.
"Do you just cut your losses and continue with another plan?"
It is not cut your losses, it is collect your wins. When someone deviates from the usual move, then there usually is a downside to that, so usually it is possible to find a move that profits from that.

Openings are really not the most important thing to care about when you are beginner, that's what pros says . But choose 1 you like and always play the it .
this 5 videos are very very very useful for beginners
it explains how to play, they help me a lot.
Chess Fundamentals #1-5 :
www.youtube.com/watch?v=Ao9iOeK_jvU&index=5&list=PLl9uuRYQ-6MBwqkmwT42l1fI7Z0bYuwwO
www.youtube.com/watch?v=TWJ6751RRis&list=PLl9uuRYQ-6MBwqkmwT42l1fI7Z0bYuwwO&index=4
www.youtube.com/watch?v=I5o2d9slUCM&list=PLl9uuRYQ-6MBwqkmwT42l1fI7Z0bYuwwO&index=3
www.youtube.com/watch?v=h-JGqEiNs-I&index=2&list=PLl9uuRYQ-6MBwqkmwT42l1fI7Z0bYuwwO
www.youtube.com/watch?v=8kdjSqNcViw&list=PLl9uuRYQ-6MBwqkmwT42l1fI7Z0bYuwwO&index=1

Thank you all for answering. I will surely watch those videos, thank you for them.