WordPress provides thousands of free or paid themes which can be installed on the website.
Here are the list of few things which you should consider when selecting a theme for WordPress:
1) Select a theme which is relevant to your business.
2) Select a responsive (mobile friendly) theme. You can do mobile friendly test here.
3) Make a list of main features you require on the website and check compatibility of major plugins such as Yoast SEO, Woocommerce( for online store), Cache plugins, Security plugins such as Wordfence with the theme.
4) Check if theme is supported for all browser types such as Chrome, Safari, Firefox etc.
5) Check compatibility of theme with the page builders such as elementor or wpbakery etc.
6) Check if your theme has SEO friendly structure.
7) Check if you theme support is good.
8) Check reviews and rating of the theme before buying it.
9) If you are going to use elementor page builder, I recommend to use Astra, Hello theme, Oceanwp.
There are many themes available at themeforest. You can choose wordpress themes which suits your business and start building an awesome website.
Feel free to get in touch if you have any questions.