Altering text in custom sidebars

Hi there,

So I am pretty new to this whole Wordpress business, but I have managed to install the twenty seventeen child theme by Jon Penland. I have 2 questions about this though:
1. With the custom sidebars I wanted to add bold text next to my pages (as you will see under 'Diensten') but I can't figure out how to style these texts. What I want to do is line them um with the column of text in the main field, but all I have managed is to insert a break..

2. With this pre-made child theme Jon Penland has added lines under the different Page titles (probably to visually seperate them from the custom sidebar), but I don't like the look of this. Whenever I try to remove this in the php, I break the site. Can you help me with removing these?

Thank you for your help!

All the best, Steef