https://www.englisch-hilfen.de/en/exercises/if_clauses/type_1_mix3.htm
https://www.englisch-hilfen.de/en/exercises/if_clauses/type_1_statements.htm
https://www.ego4u.com/en/cram-up/grammar/conditional-sentences/type-1/exercises?02
https://agendaweb.org/verbs/conditional-first-exercises.html