Why can’t I customise the texts and adjust the size of the logo?

Hi,

I download the free version recently and planning to use it for a review site. I’ve been trying to find a theme for days now where I can insert the “Search” bar on top of the sliders.
I have two questions:
1. I tried to change the texts specifically on the slider “Explore your trip” and “Let’s go wherever you want” but it seems that WP crashes after I change them.

2. I tried to insert a logo on the header (top-left). However, even how many times I photoshop and adjust the logo, it seems like it is still on the same size appearing on the website. I am unable to find the file where I can change the size.