One of the most important thing that attracts customers and viewers of any website is it's catchy design. I have list down few themes that you could use to make your website more professional. I'll be rating these themes based off of three different things 1) Ease of use 2) Clean design and 3) Customization. So depending on whether you're very beginner and you just want an easy theme or you're looking to get the most customization out of your free theme I've got your back.
Shapely
Shapely has a super clean design. This theme got parallax effect and big dividers. Too much clutter can be a bad thing so this theme really gets rid of that. And I also like that there's multiple buttons so you've got a button for pretty much anything you want to put on here which is really cool and the menu kind of sticks to the top so that's pretty cool. I tested all these themes myself and for shapely I found that you have a lot of color options actually full color control over buttons and for your text. It's also very easy to edit all you've to do is just click on the little pencil icon and it brings you right to this front page editor to edit that section. Now the con that I found with this theme is that you cannot change the font and you also cannot change the color of the header so it has to remain white but generally white is a good color because when you have obnoxious colors like purple and blue, you can get a little overwhelming so I didn't really mind that. Overall its a very beginner friendly theme and I would recommend it to anyone just starting out.
Mesmerizes
Mesmerizes's pretty cool. It's got this very colorful button designed to it, everything is really pop in. I like the nice bold action buttons because it allows people to find exactly what they want very quickly. When you activate mesmerize I highly recommend that you select the preset and put in all the sample data that it asks you to put in so it'll just give you this cool little menu set up and ask you "do you want to start the process?" just click yes. Go through it, its really simple. What I found really cool is that mesmerizes has a ton of design options. You can change the dividers to like 1M different types of dividers.You can change your button icons into any type of icon that you want. The only con I found was that you could not change the color of the button so you kinda have to stick with the color of those buttons on whatever preset that you pick but you can set your background images and all that and after you pick a preset you also have individual presets for different sections so if you have an "about me" section you can pick all these different types. If you have a header or let's say features section you can choose presets and just pop them right in.
Optimizer
Optimizer is pretty awesome. I found it to be one of the easiest themes that I've ever worked with because it has a front page editor so if you scroll down you can see it's 100% mobile responsive. It's pretty fast search engine optimize. Whenever I was editing with it like I said it's got a front page editor, it's got full color options for buttons and backgrounds. The header can actually be any color that you want they can also be transparent if you want so that's pretty cool. The whole theme actually supports woocommerce which is an extra added bonus now the small con that I found for this one is that it's not fully customizable you're actually limited to about 4 different widgets.
OceanWP
OceanWP is one of my favorite themes, I use it for my E-commerce. OceanWP is fantastic, it's got full customization and I only use oceanWP for the header and possibly the footer and I can change all the colors, text and so on. It's 100% customizable and what I do is use a page builder called elementor which is a front end page builder where you can just drag and drop different widgets and create a whole website in minutes. It is fantastic and I highly recommend it. You can change text colors, images, buttons, and add buttons all over the place if you want. So, if you're going to get oceanWP you need to get elementor. If you go to your wordpress dashboard and search for new plugins you can just search "elementor" and you could install it real quick.
Hestia
Hestia is awesome, it's super clean design, very easy to edit super beginner friendly. It even supports woocommerce which is pretty cool. Hestia is super easy to use so you just have to click on the pencil icon and you can edit any section you can change the text you can change backgrounds you can even change the colors.
If you'd like to check out any of these themes, feel free to download and start playing with them and see which one fits your website the most