Your site is looking very good! I think you have very good design skills for a developer. And as Adityaparab said in the previous comment, you are not expected to be a top designer. There are people who specialise in web design who can work with you so don’t feel you need to compete with people who have 5+ years of experience in design.
That said, I strongly believe good design skills benefit everyone and we can all improve with further work! With that in mind I’ve written some feedback that could help improve small details of your design. I think by and large the design is very successful so take my feedback with a grain of salt and decide whether you want to make any changes based on it.
Typography: Be consistent and be readable. The body text in ‘Recent Works’ is Fjalla One, whereas the body text in ‘Responsive and Aesthetically Pleasing’ is Cantarell. Cantarell is easier to read because of its body width (x-height and body width help with readability, especially on screen). The one thing the Fjalla One text has right is that it is bold. If you are reversing type (white on a darker colour) then setting it in bold helps with readability. Normal or light text can result in too little contrast visually. Looking down the rest of your page you use Fjalla One elsewhere, but it is hard to read there too. A general rule of typography is to use no more than two or three fonts in a document (sometimes you need more, but keeping it simple prevents a lot of problems). Use one font for headings, another complementary font for body text. Be consistent through the document. If you want to use a different font where you are currently using Fjalla One consider using Cantarell Bold. It will give you visual consistency with just a little bit of variety.
The blue colour theme gives a feeling of trust, reliability and tradition. I believe this works well with the site purpose. If you wanted to create a feeling of excitement, or being friendly and approachable, a different colour palette would be a good idea. You can always experiment with different colour palettes to see if anything else works for you.
Can you create rounded corners on the hover effects in the Recent Works section? On my Chrome browser the semi-opaque overlays are larger than the images beneath and don’t have the rounded corners of the images. The images themselves look nicely designed and work well with the overall site. The difference with the overlays looks jarring and it looks like you overlooked this detail. Resizing and rounding the corners may not be a big change, but a lot of design is in the details.
Consider using a larger and bolder font in your contact me button. It is your call to action and the purpose of the page. Currently it is visually less important than the tick image used to illustrate that section. Is this what you want? Don’t go overboard and make it too overwhelming, though! It’s all about visual balance.
With your testimonials - can you link to the customer’s website? This would give them an added level of trust and authenticity.
While the colour palette is largely consistent, the lighter, brighter blue in ‘I deliver high-quality products’ is a bit out of place considering you don’t seem to use it again on your page. If you are looking to include more colour variety for visual interest then try to echo that colour somewhere else in the webpage. If you are trying to keep to a strict and restrictive colour palette then look to the colours you are already using for headings and icons elsewhere and re-use them. I can’t advise you as to which approach is best. You’ll need to try it and see which works better.
Are you missing a link in your menu? It looks like you have a period mark to the left of the about link.
I hope this helps!