That depends on the qualification. A typical university degree takes 3 years. There are some foundation courses or diplomas that take less. After a degree, you might take a masters degree, which typically lasts a year. I did my first degree and masters in one go – so it was one qualification, but it took me 4 years. It depends on what area of science, too.
What Rebecca says about degrees.
I’d generally recommend wide science degrees followed by a Masters course that is more vocational over tighter first degrees. That keeps your options open.
Then for some professions (eg medicine, many others in healthcare, law) there are professional qualifications in addition to University degrees. Those can take a lot longer.
For me I took 3 years for an undergraduate degree, 1 year for my Masters degree and then 4 years for my PhD. I think all of those numbers would definitely vary if you were working part-time, which is definitely an option!