I would like to ask how the immigration officers are going to ask or what they will require once I land in Berlin. I have traveled before outside the country but this is my first time travelling as an adult and alone. What are the things that I will need?
Since you're traveling with a passport from the Philippines, you'll need a visa before you can travel (note the warning on that page about longer waiting times for appointments right now). You'll need to complete the forms and carefully follow their checklist to ensure that you've supplied all the required documents, and make an appointment to submit them to the German authorities and provide your fingerprints.
Note that you'll need to supply information about your travel plans such as the cities you plan to visit, air itinerary, and hotel reservation confirmation as detailed in the visa application guidance. You should not, however, make any non-refundable reservations until you have been issued a visa.
When you land in Berlin, you'll line up at immigration and present your passport with the visa inside. At this point, you may well get a greeting (or a grunt) and your passport stamped with no further ado. You may also be asked some questions. This answer from a related question about traveling to the UK gives you an idea of what those questions might be. They are similar to the things you should have answered in visa application. Basically, you should have a coherent itinerary for your travel, any advance reservations for transportation or lodging, a return ticket, something that proves you have the travel insurance you needed to get your visa, and access to sufficient funds (which can be through the form of bank or credit cards) to pay for your travel. It's unlikely you'll be asked about all these things, but it's good to be prepared.
Once that's all done, you'll claim any checked luggage at the baggage claim, exit out through the customs area (where there's a small chance you could be selected for a bag search), and leave the airport.
Usually you'll just be asked where you're coming from, how Long you'll be staying in Schengen for, and possibly for what purpose.
Depends on who you get on that day though - as an EU ID Card holder I have no personal experience (but often overhear non-EU nationals being checked).
As suggested above, you Need a visa for Schengen, which, for border purposes, is a single country including most EU states and all EFTA states. So, if you make a side-trip to France, Poland, Sweden, Italy, Switzerland etc. that's essentially a domestic trip (i.e. no border checks)