The code looks good. The layout is also good.
I have two design suggestions.
FIRST: Consider adding an image to the background of the <welcome-section>.
An Image can make a website look very professional, without much effort.
The code is simple:
#welcome-section {
background-image:url('https://i.imgur.com/d6tmDe3.jpg');
background-size:cover;
}
SECOND: Consider using a pre-planned color palette before you begin designing.
As a general rule, most professional websites only use about 3 main colors, and one or two accent colors.
A good place to find palettes, is a place like coolors.co: The link: coolors.co/palettes/trending
The Coolors.co site makes very easy to chose color combinations for Websites.
