I would recommend putting your bootstrap row divs within a
<div class="container"></div>, this will center your content within the page.
text-decoration: none to your anchor tags to get rid of the underlines on the hyperlinks.
background-repeat: no-repeat; background-size: cover; to your background image.
to make it look like this
Your homepage uses a serif font but your portfolio page uses a sans serif font. keep the fonts consistent across your website. You can find more interesting fonts on google fonts which is free to use. You can add selected fonts to the top of your css file using a css import like
@import url('https://fonts.googleapis.com/css2?family=Open+Sans:wght@300&display=swap'); (google fonts supplies you with the code just select the fonts you want and copy and paste it). I would go with a sans-serif font, they’re cleaner / modern.
The contact us mail link at the bottom… make this a mailto link
For the colours you might want to try https://coolors.co/, it generates colour palettes.
For design ideas use existing commercial websites that you like for inspiration. Find frontend techniques used that you think would fit your own site and try to implement them yourself.
Keep the images on the gallery page a consistent height to improve the layout, and add a margin bottom of 15px to the images - best way to do this is to crop the taller images so they are the same size as the shorter ones, that way your images aren’t squashed (as opposed to giving your images the same fixed height as I’ve done here). Also I would get rid of the text shadow on the title as it looks messy.
Definitely keep developing it, it will be a great learning experience to just focus on one real-world website like this and keep developing and improving it.