Questions & Answers about Marcus tamen fortis est et bellum non amat.
Marcus is the subject of the sentence, so it is very natural for it to come first. Latin does not rely on word order as much as English does, because endings usually show the grammar. Even so, putting the subject first is common and straightforward.
Here, Marcus is in the nominative case, which marks it as the subject.
Tamen means however, nevertheless, or still. It adds a contrast.
So the idea is something like: Marcus is brave, but despite that, he does not love war.
A learner may expect it at the very start of the sentence, but in Latin tamen often comes after the first word or early in the clause rather than standing first.
Because fortis is the correct dictionary form of this adjective. It is a third-declension adjective, not a first/second-declension one.
For the nominative singular:
- masculine: fortis
- feminine: fortis
- neuter: forte
Since Marcus is masculine singular nominative, fortis is the right form.