At once a problem: in Estonian we have a word "usk" with more or less same meaning as the German "Glaube". But there is no such word in English. "Belief" is too close to "opinion", has a hint toward relativism and subjectivity in it. But let it be. My idea is that what we call love and what we call belief (Glaube, usk, foi) are psychologically very close, nearly the same thing. Love is mostly love for a concrete person, but there have been and there are people who love persons they have never actually met. Some people love Jesus, Virgin Mary, even God himself/herself. Paradoxically, some of these people feel they have met their beloved.
We human beings are children, we never or nearly never become adults. Our needs are needs of children. In our love relationships there is a strong element of child-mother (child-parent) relationship. We need a parent figure. And if we don't have it, don't find it, we construct it. Both personally and culturally. We construct gods and spirits. We trust them, we believe they care for us, love us. And we love them.
God is our Father. We are God's children.
Love for God (Jesus, Mary) often excludes human love. Deep religious faith (religious love) doesn't tolerate erotic love. God is jealous...
Such are some of my thoughts on the subject. There is a lot to think and perhaps elaborate. For example, in the contect of hominization, our becoming who we are, intelligent beings with a big need for love. And belief.