Can somebody force my Tor circuits to always start from his "guard node", to access my traffic?

Question

The first node after "my browser" is always the same.
I am worried to see that even when asking for "new identity" or "new circuit", it restarts always by the same IP address in France. I have no knowledge on the subject. I only use Tor because my physical security has been compromised by someone who used hacking, among other means, to track me and had not stop to now. My fear is that this node could be not a random node guard but a weak one or even one belonging to the "pirate" team I try to stay hidden from. Can someone clarify please between what is really to fear and is not?

Answer 1

Yes. An attacker can perform a sybil attack or just kick down your guard node repeatedly until your Tor client choose a malicious node as guard.
Controlling your guard node doesn't lead to decrypting your traffic, but mostly makes you vulnerable to traffic correlating or path bias attacks, thus makes tagging attack and eavesdropping possible.
See Should I choose a new guard if the network is overloaded?

Answer 2

You keep using the same guard node for a long time. This is by design.
See this question: Why is a longer guard rotation period with fewer guards better than the other way around?

Even if someone has control of your guard, they can not see your traffic or tamper with it. They can only tell which middle node(s) you use.

(Besides, if someone has control over your Tor client so that they can force it to use a guard of their choosing, I imagine you are already compromised to the point that they have much easier options.)