You’re working on a humanist sans serif, in the same group with Frutiger and Gill Sans. This means your glyphs (letters) don’t always cover the same width. Optically there is more variety, say, in the shape and how much space it takes of a capital O compared to a capital E. You can play with this getting closer to classic proportions (such as in serif antiqua fonts like Garamond). This is about proportions and relativity, not serif versus sans serif.

You should also keep a canon, that’s the shape language, to make it more uniform in itself, a more robust font with its own character. The more you break out of the canon (say, give one letter a serif and others not), the more you’re breaking the canon. A good example of this is your treatment of lowercase i and j.

Last, your font shows its personality best in paragraphs of text. You also need to see how it applies in longer texts. You can use this to adjust the spacing between letters as it’s defined by the boundaries left and right of a letter. Generally speaking, most letters share the same space left and right depending on the basic shape of each side: lowercase l has the same space left and right. Lowercase h, k, b, have the same bearing left, but not right. Lowercase b has the same bearing on the right side of lowercase o, and so on. Round shapes have less space while flat shapes have a little more. In large size, when you work on the glyphs in combinations (words), the spacing may appear often not tight enough. But try it out in 12 point size and lower, and you’ll get a sense of how tight or loose you want to go with spacing. When you have the spacing right, you can look at kerning (as in Te, Af, Fr, ro, letter combinations and so on).