The subject and aim of this paper are to explain the importance of investing in the user experience and user interface design for companies and to show an example of the redesign of the website of the company called Protis.hr. The first part of the paper focuses on explaining the concept of user experience and interface design, while the second part of the paper presents the entire process of implementing these types of designs on the example of a selected company. The research methodologies used in the paper are, conducting a survey questionnaire and modelling a possible solution by developing a prototype. The research was conducted on a sample of 101 respondents, where were asked three groups of questions (general attitudes of respondents about websites, questions related to the website Protis.hr and questions related to demographic characteristics of respondents). The results of the survey additionally indicate the importance of user design experiences and interfaces. Due to the complexity of the process, in the practical part of the paper, a prototype of the title page, product offer page and description page of one of the product is presented, where the changed elements are explained in detail. By reading the theoretical and practical part of the paper, it is possible to conclude how complex and time-consuming this process actually is and how big role UX / UI design actually has for the user and the company. By investing in UX / UI design, the company not only gets a satisfied user but also results in a larger number of users, higher profits and lower costs