How to make the picture fit the place holder?

Hello Guys, I am trying to start building my portfolio but Every time I want to choose the image that is going to be in the place holder, it shows smaller. I want all the pictures to just fit in the place holder and keep the same size, but for some reason, it always changes (see attached picture) any help will be appreciated. Thanks in advance.

P.S.: Anyone knows where I can get the measurements for all the Gallery and Carousel

Placeholders are just placeholders.
You decide what size a picture is. If you want pictures all the same size you must give them the size you want BEFORE you place them in the place holder.
This may help also:

hello. thanks for the reply, but I am still confused. I am no sure why Blocs is sold as an easy software to use and now I have to go and learn all of this about classes and other things that I have been trying to avoid.

so, how do I know the size on those place holders? when I play with the classes the images that I put in there get distorted any ways (because they are different dimensions) I don’t want to have to create 2 separate batches of the same images (1 for the gallery thumbnails and another of the regular size once you open it) I just want to import them to Blocs and drop them into the place holder/container and for them to fill in the place holder without changing its size or form. it works for some images and it changes for others. This is so confusing. I just wanted a software that I could use to create easy websites without hassles and yet it gets more and more complicated by the minute. Any help will be appreciated.