Programming language as back end for web page

I have a Life Science background without any computer science background but since I am very passionate about the latter I decided to combine both. Nevertheless, sometimes its not easy to find an answer for something. Therefore my question is:

I want to write a program, that needs both strong data visualization and also computing speed. I have been working in the code, in R, for some time and its basically done. So, for the visualization is amazing but for performance, not so much, since I use some ML (not deep learning, for now) and some calculations take several minutes. For my next project I want to create a web page in which I can enter the input values and get a specific output in form of several graphs + the result of ML. For that reason I am thinking whether to continue using R for back end and improve computing speed with Rcpp and openMP (besides the inherent R tricks for computing speed improvements) or should I switch to another language like python / Java ? If there is a better way to deal with my project I would gladly hear the advice.

I know that I may be missing something of what is the best way to do web design, sorry about that.

Kind regards