How to claim travel expenses as Self-employed/Employed Seasonal worker

Good evening, I am coming across first self-assessment and struggle with definitions as foreigner, so i would rather clarify claimable travel expenses in following scenarios. I travel for different seasonal jobs across whole UK(Scotland, Wales, Lincoln Shire, Kent, Etc...), on some jobs I work as self-employed, other employed. Typically staying on farm/camp site/airBnb and then going to different working sites(fields) until season is over. Are following statements/assumptions correct? In case employer provide his way of transport, i cannot claim anything. If i must use my own car as Employee and there is nothing employer provide i can claim milage. If i am self-employed and someone would take me with his vehicle and I contribute to his fuel, can i claim milage? If I am self-employed and use my vehicle for travelling to site I can claim. Though I am very much not sure about travel across country when I move to different camp site, farm, etc. are these long travel distance claimable for the job I am about to do?

Hi Petr Kovac,
please refer to guidance at:-
Expenses if you're self-employed
and
Claim tax relief for your job expenses
Thank you.