TortoiseSVN has a nice feature where I can quickly go back to older versions in the log in my working directory, in order to quickly determine where something went wrong. It is called "Update to revision." I can't find the equivalent in TortoiseGit. Is there such an option?
Go to the log dialog an switch to a different commit.
For that use the contect menu on a comit and select "Switch/checkout to this..." (cf. https://tortoisegit.org/docs/tortoisegit/tgit-dug-showlog.html). This, by default, will create a new branch wich can be deleted afterwards.
If you are searching a revision where a bug got introduced, you should have a look at git bisect, which does a binary search on the revisions in order to find a faulty commit (cf. https://tortoisegit.org/docs/tortoisegit/tgit-dug-bisect.html).