Hi,

pretty broad question. There are many datasets available in repositories, like NMDC https://www.nmdc.no/. Here you get all kinds of data in the usual format (Darwin Core Archives or netCDF). If you are looking for sequencing data (assuming you mean extremophile microbes) then I would check ENA (https://www.ebi.ac.uk/ena/browser/) or NCBI (https://www.ncbi.nlm.nih.gov/). But there are many more around the world. Check if your country has a center. These center also often have courses or at least some documentation about how to use them and what to do with the data. And for a start up, best ask a science friend. Some of these things are tailored to specific disciplines which use specific programs etc., and so they are not easily accessible for people from outside. Which is a shame, but also has some practical reasons, like data complexity and ownership etc.

The field of bioinformatics is what we would call for using molecular data to understand more about organisms in different environments (including extreme environments). There are a number of free or relatively cheap courses online that can be used to start (Udemy has a course here.) If you search for "bioinformatic courses online" on google you should find some. Most molecular data is placed on open source repositories meaning they are available to everyone. Other datasets as mentioned in the other post can sometimes be hard to acquire not through an institution, but this is changing slowly to be more open I would say.

Many questions can be answered using this data, I would say the difficult thing is defining the question - there is so much data it is easy to get lost when exploring it. You might be interested in understanding if x species of bacteria is affected by temperature, or if the total microbial community is different between different kinds of ice - these are all things you could answer with this data.