You are asking for engineering advice that could well be taken out of context by your or others reading this later. That makes it difficult to answer.
The present supports are considered enough to hold the overhang. Replacing them with something similar on a temporary basis will probably work.
There are presently 3 columns holding up the roof that look like 4x4s. Based on the pictures, you are in a region where snow load is considered. Assuming
there is a beam that goes from column to column or at least a trussed rafter, you can probably remove the middle column for a short period of time without failure if you put no extra load on the roof. You might get some sag over the length and that could possibly stress the roof and cause problems. Without knowing the construction and the loads, I wouldn't suggest it.
Because you want a clear area under the overhang you need to replace the posts with a support that goes outside the porch area. The simplest way to do that is a beam that spans the porch with posts holding up each end. Simple to put up if you know what you are doing. Not so simple to calculate the required strength and sizes from photographs. Your beam has to be strong enough to hold the load and not sag or flex. The posts have to be securely anchored and strong enough to support the beam. Do any of it wrong and the roof could fall on you while jackhammering concrete risking injury and death.
A contractor might come in with a steel i-beam and screw jack supports for each end. This would allow them to raise the roof enough to remove the wooden columns. Removing the existing columns also needs to be considered in how you support the roof. Your temporary support has to allow for removal of the existing supports.
I would never use 2x4 for making a beam to hold anything up. When making a beam any 2x should probably be doubled up to make a 4x. Always use the strength of the wood wherever possible. Don't rely on nails or screws for vertical support unless you understand the technique. It's always better and safer to over engineer for strength.
Know what the weakest point is. That is what will fail if something does fail. It doesn't do any good to use 2 2x12's for a beam and then only use a couple of nails to attach them to the side of a 4x6 column.
A general rule for temporary supports is if you use similar materials and construction as the permanent support you will be strong enough. Just make sure it is all solidly tied in.