Question on conjugation and use of se, le and la

[Tony123]

Hello there. I’m looking for some guidance on what I need to study to get my head around the use of se, le and el/la.
This sentence, for example: “Se le tomaron las huellas y se la dejó ir a casa.”
In the phrase “se le tomaron las huellas” - I don’t know what the “se” represents. Does it mean “them”? I.e. if I was reading this in English would it translate to “they took them (se) from her (le), the fingerprints” If I was trying to say this myself I would have said “tomaron sus huellas” or “tomaron las huellas de ella”.
In the second part of the sentence “se la dejó ir a casa”, I have no idea what “se” represents. I would have written it as “la dejó ir a casa”. In fact I wold have written it as “le dejó ir a casa”. That is the second part of my question. When and where should I represent a person as le (as with the first part of the sentence) versus when should I use el/la (as with the second part)? I would really be grateful for someone to help me understand this better! Even if just to direct me to a useful resource. I’m sorry if I’m using the wrong terminology.