Can you please elaborate on what type of samples and from where you can download them?

I agree with MSRS. Do you want to download your own data or publicly available?

For publicly available you can always get data from ENA (fastq or bam format), or SRA (can be .SRA format and you need to convert to fastq).

To read fastq you can use cat | less or zcat | less for fastq.gz. For bam I suggest you use samtools functions.

Where have you looked? What have you tried?